src/HOL/List.thy
author wenzelm
Tue Mar 13 13:31:26 2012 +0100 (2012-03-13)
changeset 46898 1570b30ee040
parent 46884 154dc6ec0041
child 47108 2a1953f0d20d
permissions -rw-r--r--
tuned proofs -- eliminated pointless chaining of facts after 'interpret';
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(*  Title:      HOL/List.thy
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    Author:     Tobias Nipkow
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*)
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header {* The datatype of finite lists *}
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theory List
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imports Plain Presburger Code_Numeral Quotient ATP
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uses
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  ("Tools/list_code.ML")
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  ("Tools/list_to_set_comprehension.ML")
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begin
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datatype 'a list =
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    Nil    ("[]")
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  | Cons 'a  "'a list"    (infixr "#" 65)
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syntax
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  -- {* list Enumeration *}
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  "_list" :: "args => 'a list"    ("[(_)]")
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translations
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  "[x, xs]" == "x#[xs]"
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  "[x]" == "x#[]"
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subsection {* Basic list processing functions *}
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primrec
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  hd :: "'a list \<Rightarrow> 'a" where
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  "hd (x # xs) = x"
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primrec
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  tl :: "'a list \<Rightarrow> 'a list" where
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    "tl [] = []"
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  | "tl (x # xs) = xs"
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primrec
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  last :: "'a list \<Rightarrow> 'a" where
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  "last (x # xs) = (if xs = [] then x else last xs)"
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primrec
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  butlast :: "'a list \<Rightarrow> 'a list" where
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    "butlast []= []"
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  | "butlast (x # xs) = (if xs = [] then [] else x # butlast xs)"
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primrec
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  set :: "'a list \<Rightarrow> 'a set" where
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    "set [] = {}"
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  | "set (x # xs) = insert x (set xs)"
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definition
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  coset :: "'a list \<Rightarrow> 'a set" where
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  [simp]: "coset xs = - set xs"
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primrec
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  map :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a list \<Rightarrow> 'b list" where
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    "map f [] = []"
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  | "map f (x # xs) = f x # map f xs"
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primrec
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  append :: "'a list \<Rightarrow> 'a list \<Rightarrow> 'a list" (infixr "@" 65) where
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    append_Nil:"[] @ ys = ys"
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  | append_Cons: "(x#xs) @ ys = x # xs @ ys"
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primrec
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  rev :: "'a list \<Rightarrow> 'a list" where
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    "rev [] = []"
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  | "rev (x # xs) = rev xs @ [x]"
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primrec
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  filter:: "('a \<Rightarrow> bool) \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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    "filter P [] = []"
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  | "filter P (x # xs) = (if P x then x # filter P xs else filter P xs)"
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syntax
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  -- {* Special syntax for filter *}
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  "_filter" :: "[pttrn, 'a list, bool] => 'a list"    ("(1[_<-_./ _])")
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translations
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  "[x<-xs . P]"== "CONST filter (%x. P) xs"
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syntax (xsymbols)
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  "_filter" :: "[pttrn, 'a list, bool] => 'a list"("(1[_\<leftarrow>_ ./ _])")
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syntax (HTML output)
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  "_filter" :: "[pttrn, 'a list, bool] => 'a list"("(1[_\<leftarrow>_ ./ _])")
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primrec -- {* canonical argument order *}
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  fold :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'a list \<Rightarrow> 'b \<Rightarrow> 'b" where
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    "fold f [] = id"
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  | "fold f (x # xs) = fold f xs \<circ> f x"
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definition 
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  foldr :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'a list \<Rightarrow> 'b \<Rightarrow> 'b" where
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  [code_abbrev]: "foldr f xs = fold f (rev xs)"
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definition
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  foldl :: "('b \<Rightarrow> 'a \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a list \<Rightarrow> 'b" where
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  "foldl f s xs = fold (\<lambda>x s. f s x)  xs s"
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primrec
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  concat:: "'a list list \<Rightarrow> 'a list" where
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    "concat [] = []"
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  | "concat (x # xs) = x @ concat xs"
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definition (in monoid_add)
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  listsum :: "'a list \<Rightarrow> 'a" where
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  "listsum xs = foldr plus xs 0"
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primrec
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  drop:: "nat \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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    drop_Nil: "drop n [] = []"
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  | drop_Cons: "drop n (x # xs) = (case n of 0 \<Rightarrow> x # xs | Suc m \<Rightarrow> drop m xs)"
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  -- {*Warning: simpset does not contain this definition, but separate
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       theorems for @{text "n = 0"} and @{text "n = Suc k"} *}
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primrec
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  take:: "nat \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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    take_Nil:"take n [] = []"
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  | take_Cons: "take n (x # xs) = (case n of 0 \<Rightarrow> [] | Suc m \<Rightarrow> x # take m xs)"
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  -- {*Warning: simpset does not contain this definition, but separate
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       theorems for @{text "n = 0"} and @{text "n = Suc k"} *}
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primrec
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  nth :: "'a list => nat => 'a" (infixl "!" 100) where
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  nth_Cons: "(x # xs) ! n = (case n of 0 \<Rightarrow> x | Suc k \<Rightarrow> xs ! k)"
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  -- {*Warning: simpset does not contain this definition, but separate
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       theorems for @{text "n = 0"} and @{text "n = Suc k"} *}
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primrec
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  list_update :: "'a list \<Rightarrow> nat \<Rightarrow> 'a \<Rightarrow> 'a list" where
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    "list_update [] i v = []"
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  | "list_update (x # xs) i v = (case i of 0 \<Rightarrow> v # xs | Suc j \<Rightarrow> x # list_update xs j v)"
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nonterminal lupdbinds and lupdbind
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syntax
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  "_lupdbind":: "['a, 'a] => lupdbind"    ("(2_ :=/ _)")
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  "" :: "lupdbind => lupdbinds"    ("_")
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  "_lupdbinds" :: "[lupdbind, lupdbinds] => lupdbinds"    ("_,/ _")
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  "_LUpdate" :: "['a, lupdbinds] => 'a"    ("_/[(_)]" [900,0] 900)
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translations
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  "_LUpdate xs (_lupdbinds b bs)" == "_LUpdate (_LUpdate xs b) bs"
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  "xs[i:=x]" == "CONST list_update xs i x"
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primrec
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  takeWhile :: "('a \<Rightarrow> bool) \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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    "takeWhile P [] = []"
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  | "takeWhile P (x # xs) = (if P x then x # takeWhile P xs else [])"
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primrec
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  dropWhile :: "('a \<Rightarrow> bool) \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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    "dropWhile P [] = []"
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  | "dropWhile P (x # xs) = (if P x then dropWhile P xs else x # xs)"
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primrec
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  zip :: "'a list \<Rightarrow> 'b list \<Rightarrow> ('a \<times> 'b) list" where
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    "zip xs [] = []"
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  | zip_Cons: "zip xs (y # ys) = (case xs of [] => [] | z # zs => (z, y) # zip zs ys)"
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  -- {*Warning: simpset does not contain this definition, but separate
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       theorems for @{text "xs = []"} and @{text "xs = z # zs"} *}
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primrec 
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  upt :: "nat \<Rightarrow> nat \<Rightarrow> nat list" ("(1[_..</_'])") where
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    upt_0: "[i..<0] = []"
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  | upt_Suc: "[i..<(Suc j)] = (if i <= j then [i..<j] @ [j] else [])"
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definition
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  insert :: "'a \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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  "insert x xs = (if x \<in> set xs then xs else x # xs)"
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hide_const (open) insert
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hide_fact (open) insert_def
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primrec
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  remove1 :: "'a \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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    "remove1 x [] = []"
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  | "remove1 x (y # xs) = (if x = y then xs else y # remove1 x xs)"
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primrec
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  removeAll :: "'a \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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    "removeAll x [] = []"
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  | "removeAll x (y # xs) = (if x = y then removeAll x xs else y # removeAll x xs)"
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primrec
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  distinct :: "'a list \<Rightarrow> bool" where
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    "distinct [] \<longleftrightarrow> True"
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  | "distinct (x # xs) \<longleftrightarrow> x \<notin> set xs \<and> distinct xs"
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primrec
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  remdups :: "'a list \<Rightarrow> 'a list" where
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    "remdups [] = []"
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  | "remdups (x # xs) = (if x \<in> set xs then remdups xs else x # remdups xs)"
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primrec
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  replicate :: "nat \<Rightarrow> 'a \<Rightarrow> 'a list" where
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    replicate_0: "replicate 0 x = []"
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  | replicate_Suc: "replicate (Suc n) x = x # replicate n x"
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text {*
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  Function @{text size} is overloaded for all datatypes. Users may
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  refer to the list version as @{text length}. *}
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abbreviation
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  length :: "'a list \<Rightarrow> nat" where
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  "length \<equiv> size"
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primrec rotate1 :: "'a list \<Rightarrow> 'a list" where
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  "rotate1 [] = []" |
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  "rotate1 (x # xs) = xs @ [x]"
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definition
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  rotate :: "nat \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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  "rotate n = rotate1 ^^ n"
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definition
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  list_all2 :: "('a => 'b => bool) => 'a list => 'b list => bool" where
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  "list_all2 P xs ys =
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    (length xs = length ys \<and> (\<forall>(x, y) \<in> set (zip xs ys). P x y))"
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definition
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  sublist :: "'a list => nat set => 'a list" where
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  "sublist xs A = map fst (filter (\<lambda>p. snd p \<in> A) (zip xs [0..<size xs]))"
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fun splice :: "'a list \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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"splice [] ys = ys" |
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"splice xs [] = xs" |
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"splice (x#xs) (y#ys) = x # y # splice xs ys"
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text{*
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\begin{figure}[htbp]
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\fbox{
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\begin{tabular}{l}
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@{lemma "[a,b]@[c,d] = [a,b,c,d]" by simp}\\
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@{lemma "length [a,b,c] = 3" by simp}\\
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@{lemma "set [a,b,c] = {a,b,c}" by simp}\\
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@{lemma "map f [a,b,c] = [f a, f b, f c]" by simp}\\
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@{lemma "rev [a,b,c] = [c,b,a]" by simp}\\
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@{lemma "hd [a,b,c,d] = a" by simp}\\
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@{lemma "tl [a,b,c,d] = [b,c,d]" by simp}\\
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@{lemma "last [a,b,c,d] = d" by simp}\\
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@{lemma "butlast [a,b,c,d] = [a,b,c]" by simp}\\
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@{lemma[source] "filter (\<lambda>n::nat. n<2) [0,2,1] = [0,1]" by simp}\\
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@{lemma "concat [[a,b],[c,d,e],[],[f]] = [a,b,c,d,e,f]" by simp}\\
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@{lemma "fold f [a,b,c] x = f c (f b (f a x))" by simp}\\
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@{lemma "foldr f [a,b,c] x = f a (f b (f c x))" by (simp add: foldr_def)}\\
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@{lemma "foldl f x [a,b,c] = f (f (f x a) b) c" by (simp add: foldl_def)}\\
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@{lemma "zip [a,b,c] [x,y,z] = [(a,x),(b,y),(c,z)]" by simp}\\
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@{lemma "zip [a,b] [x,y,z] = [(a,x),(b,y)]" by simp}\\
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@{lemma "splice [a,b,c] [x,y,z] = [a,x,b,y,c,z]" by simp}\\
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@{lemma "splice [a,b,c,d] [x,y] = [a,x,b,y,c,d]" by simp}\\
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@{lemma "take 2 [a,b,c,d] = [a,b]" by simp}\\
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@{lemma "take 6 [a,b,c,d] = [a,b,c,d]" by simp}\\
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@{lemma "drop 2 [a,b,c,d] = [c,d]" by simp}\\
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@{lemma "drop 6 [a,b,c,d] = []" by simp}\\
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@{lemma "takeWhile (%n::nat. n<3) [1,2,3,0] = [1,2]" by simp}\\
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@{lemma "dropWhile (%n::nat. n<3) [1,2,3,0] = [3,0]" by simp}\\
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@{lemma "distinct [2,0,1::nat]" by simp}\\
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@{lemma "remdups [2,0,2,1::nat,2] = [0,1,2]" by simp}\\
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@{lemma "List.insert 2 [0::nat,1,2] = [0,1,2]" by (simp add: List.insert_def)}\\
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@{lemma "List.insert 3 [0::nat,1,2] = [3,0,1,2]" by (simp add: List.insert_def)}\\
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@{lemma "remove1 2 [2,0,2,1::nat,2] = [0,2,1,2]" by simp}\\
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@{lemma "removeAll 2 [2,0,2,1::nat,2] = [0,1]" by simp}\\
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@{lemma "nth [a,b,c,d] 2 = c" by simp}\\
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@{lemma "[a,b,c,d][2 := x] = [a,b,x,d]" by simp}\\
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@{lemma "sublist [a,b,c,d,e] {0,2,3} = [a,c,d]" by (simp add:sublist_def)}\\
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@{lemma "rotate1 [a,b,c,d] = [b,c,d,a]" by simp}\\
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@{lemma "rotate 3 [a,b,c,d] = [d,a,b,c]" by (simp add:rotate_def eval_nat_numeral)}\\
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@{lemma "replicate 4 a = [a,a,a,a]" by (simp add:eval_nat_numeral)}\\
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@{lemma "[2..<5] = [2,3,4]" by (simp add:eval_nat_numeral)}\\
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@{lemma "listsum [1,2,3::nat] = 6" by (simp add: listsum_def foldr_def)}
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\end{tabular}}
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\caption{Characteristic examples}
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\label{fig:Characteristic}
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\end{figure}
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Figure~\ref{fig:Characteristic} shows characteristic examples
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that should give an intuitive understanding of the above functions.
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*}
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text{* The following simple sort functions are intended for proofs,
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not for efficient implementations. *}
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context linorder
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begin
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inductive sorted :: "'a list \<Rightarrow> bool" where
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  Nil [iff]: "sorted []"
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| Cons: "\<forall>y\<in>set xs. x \<le> y \<Longrightarrow> sorted xs \<Longrightarrow> sorted (x # xs)"
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lemma sorted_single [iff]:
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  "sorted [x]"
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  by (rule sorted.Cons) auto
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lemma sorted_many:
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  "x \<le> y \<Longrightarrow> sorted (y # zs) \<Longrightarrow> sorted (x # y # zs)"
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  by (rule sorted.Cons) (cases "y # zs" rule: sorted.cases, auto)
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lemma sorted_many_eq [simp, code]:
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  "sorted (x # y # zs) \<longleftrightarrow> x \<le> y \<and> sorted (y # zs)"
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  by (auto intro: sorted_many elim: sorted.cases)
haftmann@39915
   302
haftmann@39915
   303
lemma [code]:
haftmann@39915
   304
  "sorted [] \<longleftrightarrow> True"
haftmann@39915
   305
  "sorted [x] \<longleftrightarrow> True"
haftmann@39915
   306
  by simp_all
nipkow@24697
   307
hoelzl@33639
   308
primrec insort_key :: "('b \<Rightarrow> 'a) \<Rightarrow> 'b \<Rightarrow> 'b list \<Rightarrow> 'b list" where
haftmann@46133
   309
  "insort_key f x [] = [x]" |
haftmann@46133
   310
  "insort_key f x (y#ys) = (if f x \<le> f y then (x#y#ys) else y#(insort_key f x ys))"
hoelzl@33639
   311
haftmann@35195
   312
definition sort_key :: "('b \<Rightarrow> 'a) \<Rightarrow> 'b list \<Rightarrow> 'b list" where
haftmann@46133
   313
  "sort_key f xs = foldr (insort_key f) xs []"
hoelzl@33639
   314
haftmann@40210
   315
definition insort_insert_key :: "('b \<Rightarrow> 'a) \<Rightarrow> 'b \<Rightarrow> 'b list \<Rightarrow> 'b list" where
haftmann@40210
   316
  "insort_insert_key f x xs = (if f x \<in> f ` set xs then xs else insort_key f x xs)"
haftmann@40210
   317
hoelzl@33639
   318
abbreviation "sort \<equiv> sort_key (\<lambda>x. x)"
hoelzl@33639
   319
abbreviation "insort \<equiv> insort_key (\<lambda>x. x)"
haftmann@40210
   320
abbreviation "insort_insert \<equiv> insort_insert_key (\<lambda>x. x)"
haftmann@35608
   321
wenzelm@25221
   322
end
wenzelm@25221
   323
nipkow@24616
   324
wenzelm@23388
   325
subsubsection {* List comprehension *}
nipkow@23192
   326
nipkow@24349
   327
text{* Input syntax for Haskell-like list comprehension notation.
nipkow@24349
   328
Typical example: @{text"[(x,y). x \<leftarrow> xs, y \<leftarrow> ys, x \<noteq> y]"},
nipkow@24349
   329
the list of all pairs of distinct elements from @{text xs} and @{text ys}.
nipkow@24349
   330
The syntax is as in Haskell, except that @{text"|"} becomes a dot
nipkow@24349
   331
(like in Isabelle's set comprehension): @{text"[e. x \<leftarrow> xs, \<dots>]"} rather than
nipkow@24349
   332
\verb![e| x <- xs, ...]!.
nipkow@24349
   333
nipkow@24349
   334
The qualifiers after the dot are
nipkow@24349
   335
\begin{description}
nipkow@24349
   336
\item[generators] @{text"p \<leftarrow> xs"},
nipkow@24476
   337
 where @{text p} is a pattern and @{text xs} an expression of list type, or
nipkow@24476
   338
\item[guards] @{text"b"}, where @{text b} is a boolean expression.
nipkow@24476
   339
%\item[local bindings] @ {text"let x = e"}.
nipkow@24349
   340
\end{description}
nipkow@23240
   341
nipkow@24476
   342
Just like in Haskell, list comprehension is just a shorthand. To avoid
nipkow@24476
   343
misunderstandings, the translation into desugared form is not reversed
nipkow@24476
   344
upon output. Note that the translation of @{text"[e. x \<leftarrow> xs]"} is
nipkow@24476
   345
optmized to @{term"map (%x. e) xs"}.
nipkow@23240
   346
nipkow@24349
   347
It is easy to write short list comprehensions which stand for complex
nipkow@24349
   348
expressions. During proofs, they may become unreadable (and
nipkow@24349
   349
mangled). In such cases it can be advisable to introduce separate
nipkow@24349
   350
definitions for the list comprehensions in question.  *}
nipkow@24349
   351
wenzelm@46138
   352
nonterminal lc_qual and lc_quals
nipkow@23192
   353
nipkow@23192
   354
syntax
wenzelm@46138
   355
  "_listcompr" :: "'a \<Rightarrow> lc_qual \<Rightarrow> lc_quals \<Rightarrow> 'a list"  ("[_ . __")
wenzelm@46138
   356
  "_lc_gen" :: "'a \<Rightarrow> 'a list \<Rightarrow> lc_qual"  ("_ <- _")
wenzelm@46138
   357
  "_lc_test" :: "bool \<Rightarrow> lc_qual" ("_")
wenzelm@46138
   358
  (*"_lc_let" :: "letbinds => lc_qual"  ("let _")*)
wenzelm@46138
   359
  "_lc_end" :: "lc_quals" ("]")
wenzelm@46138
   360
  "_lc_quals" :: "lc_qual \<Rightarrow> lc_quals \<Rightarrow> lc_quals"  (", __")
wenzelm@46138
   361
  "_lc_abs" :: "'a => 'b list => 'b list"
nipkow@23192
   362
nipkow@24476
   363
(* These are easier than ML code but cannot express the optimized
nipkow@24476
   364
   translation of [e. p<-xs]
nipkow@23192
   365
translations
wenzelm@46138
   366
  "[e. p<-xs]" => "concat(map (_lc_abs p [e]) xs)"
wenzelm@46138
   367
  "_listcompr e (_lc_gen p xs) (_lc_quals Q Qs)"
wenzelm@46138
   368
   => "concat (map (_lc_abs p (_listcompr e Q Qs)) xs)"
wenzelm@46138
   369
  "[e. P]" => "if P then [e] else []"
wenzelm@46138
   370
  "_listcompr e (_lc_test P) (_lc_quals Q Qs)"
wenzelm@46138
   371
   => "if P then (_listcompr e Q Qs) else []"
wenzelm@46138
   372
  "_listcompr e (_lc_let b) (_lc_quals Q Qs)"
wenzelm@46138
   373
   => "_Let b (_listcompr e Q Qs)"
nipkow@24476
   374
*)
nipkow@23240
   375
nipkow@23279
   376
syntax (xsymbols)
wenzelm@46138
   377
  "_lc_gen" :: "'a \<Rightarrow> 'a list \<Rightarrow> lc_qual"  ("_ \<leftarrow> _")
nipkow@23279
   378
syntax (HTML output)
wenzelm@46138
   379
  "_lc_gen" :: "'a \<Rightarrow> 'a list \<Rightarrow> lc_qual"  ("_ \<leftarrow> _")
nipkow@24349
   380
nipkow@24349
   381
parse_translation (advanced) {*
wenzelm@46138
   382
  let
wenzelm@46138
   383
    val NilC = Syntax.const @{const_syntax Nil};
wenzelm@46138
   384
    val ConsC = Syntax.const @{const_syntax Cons};
wenzelm@46138
   385
    val mapC = Syntax.const @{const_syntax map};
wenzelm@46138
   386
    val concatC = Syntax.const @{const_syntax concat};
wenzelm@46138
   387
    val IfC = Syntax.const @{const_syntax If};
wenzelm@46138
   388
wenzelm@46138
   389
    fun single x = ConsC $ x $ NilC;
wenzelm@46138
   390
wenzelm@46138
   391
    fun pat_tr ctxt p e opti = (* %x. case x of p => e | _ => [] *)
wenzelm@46138
   392
      let
wenzelm@46138
   393
        (* FIXME proper name context!? *)
wenzelm@46138
   394
        val x =
wenzelm@46138
   395
          Free (singleton (Name.variant_list (fold Term.add_free_names [p, e] [])) "x", dummyT);
wenzelm@46138
   396
        val e = if opti then single e else e;
wenzelm@46138
   397
        val case1 = Syntax.const @{syntax_const "_case1"} $ p $ e;
wenzelm@46138
   398
        val case2 =
wenzelm@46138
   399
          Syntax.const @{syntax_const "_case1"} $
wenzelm@46138
   400
            Syntax.const @{const_syntax dummy_pattern} $ NilC;
wenzelm@46138
   401
        val cs = Syntax.const @{syntax_const "_case2"} $ case1 $ case2;
wenzelm@46138
   402
      in Syntax_Trans.abs_tr [x, Datatype_Case.case_tr false ctxt [x, cs]] end;
wenzelm@46138
   403
wenzelm@46138
   404
    fun abs_tr ctxt p e opti =
wenzelm@46138
   405
      (case Term_Position.strip_positions p of
wenzelm@46138
   406
        Free (s, T) =>
wenzelm@46138
   407
          let
wenzelm@46138
   408
            val thy = Proof_Context.theory_of ctxt;
wenzelm@46138
   409
            val s' = Proof_Context.intern_const ctxt s;
wenzelm@46138
   410
          in
wenzelm@46138
   411
            if Sign.declared_const thy s'
wenzelm@46138
   412
            then (pat_tr ctxt p e opti, false)
wenzelm@46138
   413
            else (Syntax_Trans.abs_tr [p, e], true)
wenzelm@46138
   414
          end
wenzelm@46138
   415
      | _ => (pat_tr ctxt p e opti, false));
wenzelm@46138
   416
wenzelm@46138
   417
    fun lc_tr ctxt [e, Const (@{syntax_const "_lc_test"}, _) $ b, qs] =
wenzelm@46138
   418
          let
wenzelm@46138
   419
            val res =
wenzelm@46138
   420
              (case qs of
wenzelm@46138
   421
                Const (@{syntax_const "_lc_end"}, _) => single e
wenzelm@46138
   422
              | Const (@{syntax_const "_lc_quals"}, _) $ q $ qs => lc_tr ctxt [e, q, qs]);
wenzelm@46138
   423
          in IfC $ b $ res $ NilC end
wenzelm@46138
   424
      | lc_tr ctxt
wenzelm@46138
   425
            [e, Const (@{syntax_const "_lc_gen"}, _) $ p $ es,
wenzelm@46138
   426
              Const(@{syntax_const "_lc_end"}, _)] =
wenzelm@46138
   427
          (case abs_tr ctxt p e true of
wenzelm@46138
   428
            (f, true) => mapC $ f $ es
wenzelm@46138
   429
          | (f, false) => concatC $ (mapC $ f $ es))
wenzelm@46138
   430
      | lc_tr ctxt
wenzelm@46138
   431
            [e, Const (@{syntax_const "_lc_gen"}, _) $ p $ es,
wenzelm@46138
   432
              Const (@{syntax_const "_lc_quals"}, _) $ q $ qs] =
wenzelm@46138
   433
          let val e' = lc_tr ctxt [e, q, qs];
wenzelm@46138
   434
          in concatC $ (mapC $ (fst (abs_tr ctxt p e' false)) $ es) end;
wenzelm@46138
   435
wenzelm@46138
   436
  in [(@{syntax_const "_listcompr"}, lc_tr)] end
nipkow@24349
   437
*}
nipkow@23279
   438
wenzelm@42167
   439
ML {*
wenzelm@42167
   440
  let
wenzelm@42167
   441
    val read = Syntax.read_term @{context};
wenzelm@42167
   442
    fun check s1 s2 = read s1 aconv read s2 orelse error ("Check failed: " ^ quote s1);
wenzelm@42167
   443
  in
wenzelm@42167
   444
    check "[(x,y,z). b]" "if b then [(x, y, z)] else []";
wenzelm@42167
   445
    check "[(x,y,z). x\<leftarrow>xs]" "map (\<lambda>x. (x, y, z)) xs";
wenzelm@42167
   446
    check "[e x y. x\<leftarrow>xs, y\<leftarrow>ys]" "concat (map (\<lambda>x. map (\<lambda>y. e x y) ys) xs)";
wenzelm@42167
   447
    check "[(x,y,z). x<a, x>b]" "if x < a then if b < x then [(x, y, z)] else [] else []";
wenzelm@42167
   448
    check "[(x,y,z). x\<leftarrow>xs, x>b]" "concat (map (\<lambda>x. if b < x then [(x, y, z)] else []) xs)";
wenzelm@42167
   449
    check "[(x,y,z). x<a, x\<leftarrow>xs]" "if x < a then map (\<lambda>x. (x, y, z)) xs else []";
wenzelm@42167
   450
    check "[(x,y). Cons True x \<leftarrow> xs]"
wenzelm@42167
   451
      "concat (map (\<lambda>xa. case xa of [] \<Rightarrow> [] | True # x \<Rightarrow> [(x, y)] | False # x \<Rightarrow> []) xs)";
wenzelm@42167
   452
    check "[(x,y,z). Cons x [] \<leftarrow> xs]"
wenzelm@42167
   453
      "concat (map (\<lambda>xa. case xa of [] \<Rightarrow> [] | [x] \<Rightarrow> [(x, y, z)] | x # aa # lista \<Rightarrow> []) xs)";
wenzelm@42167
   454
    check "[(x,y,z). x<a, x>b, x=d]"
wenzelm@42167
   455
      "if x < a then if b < x then if x = d then [(x, y, z)] else [] else [] else []";
wenzelm@42167
   456
    check "[(x,y,z). x<a, x>b, y\<leftarrow>ys]"
wenzelm@42167
   457
      "if x < a then if b < x then map (\<lambda>y. (x, y, z)) ys else [] else []";
wenzelm@42167
   458
    check "[(x,y,z). x<a, x\<leftarrow>xs,y>b]"
wenzelm@42167
   459
      "if x < a then concat (map (\<lambda>x. if b < y then [(x, y, z)] else []) xs) else []";
wenzelm@42167
   460
    check "[(x,y,z). x<a, x\<leftarrow>xs, y\<leftarrow>ys]"
wenzelm@42167
   461
      "if x < a then concat (map (\<lambda>x. map (\<lambda>y. (x, y, z)) ys) xs) else []";
wenzelm@42167
   462
    check "[(x,y,z). x\<leftarrow>xs, x>b, y<a]"
wenzelm@42167
   463
      "concat (map (\<lambda>x. if b < x then if y < a then [(x, y, z)] else [] else []) xs)";
wenzelm@42167
   464
    check "[(x,y,z). x\<leftarrow>xs, x>b, y\<leftarrow>ys]"
wenzelm@42167
   465
      "concat (map (\<lambda>x. if b < x then map (\<lambda>y. (x, y, z)) ys else []) xs)";
wenzelm@42167
   466
    check "[(x,y,z). x\<leftarrow>xs, y\<leftarrow>ys,y>x]"
wenzelm@42167
   467
      "concat (map (\<lambda>x. concat (map (\<lambda>y. if x < y then [(x, y, z)] else []) ys)) xs)";
wenzelm@42167
   468
    check "[(x,y,z). x\<leftarrow>xs, y\<leftarrow>ys,z\<leftarrow>zs]"
wenzelm@42167
   469
      "concat (map (\<lambda>x. concat (map (\<lambda>y. map (\<lambda>z. (x, y, z)) zs) ys)) xs)"
wenzelm@42167
   470
  end;
wenzelm@42167
   471
*}
wenzelm@42167
   472
wenzelm@35115
   473
(*
nipkow@24349
   474
term "[(x,y). x\<leftarrow>xs, let xx = x+x, y\<leftarrow>ys, y \<noteq> xx]"
nipkow@23192
   475
*)
nipkow@23192
   476
wenzelm@42167
   477
bulwahn@41463
   478
use "Tools/list_to_set_comprehension.ML"
bulwahn@41463
   479
bulwahn@41463
   480
simproc_setup list_to_set_comprehension ("set xs") = {* K List_to_Set_Comprehension.simproc *}
bulwahn@41463
   481
haftmann@46133
   482
code_datatype set coset
haftmann@46133
   483
haftmann@46133
   484
hide_const (open) coset
wenzelm@35115
   485
haftmann@21061
   486
subsubsection {* @{const Nil} and @{const Cons} *}
haftmann@21061
   487
haftmann@21061
   488
lemma not_Cons_self [simp]:
haftmann@21061
   489
  "xs \<noteq> x # xs"
nipkow@13145
   490
by (induct xs) auto
wenzelm@13114
   491
wenzelm@41697
   492
lemma not_Cons_self2 [simp]:
wenzelm@41697
   493
  "x # xs \<noteq> xs"
wenzelm@41697
   494
by (rule not_Cons_self [symmetric])
wenzelm@13114
   495
wenzelm@13142
   496
lemma neq_Nil_conv: "(xs \<noteq> []) = (\<exists>y ys. xs = y # ys)"
nipkow@13145
   497
by (induct xs) auto
wenzelm@13114
   498
wenzelm@13142
   499
lemma length_induct:
haftmann@21061
   500
  "(\<And>xs. \<forall>ys. length ys < length xs \<longrightarrow> P ys \<Longrightarrow> P xs) \<Longrightarrow> P xs"
nipkow@17589
   501
by (rule measure_induct [of length]) iprover
wenzelm@13114
   502
haftmann@37289
   503
lemma list_nonempty_induct [consumes 1, case_names single cons]:
haftmann@37289
   504
  assumes "xs \<noteq> []"
haftmann@37289
   505
  assumes single: "\<And>x. P [x]"
haftmann@37289
   506
  assumes cons: "\<And>x xs. xs \<noteq> [] \<Longrightarrow> P xs \<Longrightarrow> P (x # xs)"
haftmann@37289
   507
  shows "P xs"
haftmann@37289
   508
using `xs \<noteq> []` proof (induct xs)
haftmann@37289
   509
  case Nil then show ?case by simp
haftmann@37289
   510
next
haftmann@37289
   511
  case (Cons x xs) show ?case proof (cases xs)
haftmann@37289
   512
    case Nil with single show ?thesis by simp
haftmann@37289
   513
  next
haftmann@37289
   514
    case Cons then have "xs \<noteq> []" by simp
haftmann@37289
   515
    moreover with Cons.hyps have "P xs" .
haftmann@37289
   516
    ultimately show ?thesis by (rule cons)
haftmann@37289
   517
  qed
haftmann@37289
   518
qed
haftmann@37289
   519
hoelzl@45714
   520
lemma inj_split_Cons: "inj_on (\<lambda>(xs, n). n#xs) X"
hoelzl@45714
   521
  by (auto intro!: inj_onI)
wenzelm@13114
   522
haftmann@21061
   523
subsubsection {* @{const length} *}
wenzelm@13114
   524
wenzelm@13142
   525
text {*
haftmann@21061
   526
  Needs to come before @{text "@"} because of theorem @{text
haftmann@21061
   527
  append_eq_append_conv}.
wenzelm@13142
   528
*}
wenzelm@13114
   529
wenzelm@13142
   530
lemma length_append [simp]: "length (xs @ ys) = length xs + length ys"
nipkow@13145
   531
by (induct xs) auto
wenzelm@13114
   532
wenzelm@13142
   533
lemma length_map [simp]: "length (map f xs) = length xs"
nipkow@13145
   534
by (induct xs) auto
wenzelm@13114
   535
wenzelm@13142
   536
lemma length_rev [simp]: "length (rev xs) = length xs"
nipkow@13145
   537
by (induct xs) auto
wenzelm@13114
   538
wenzelm@13142
   539
lemma length_tl [simp]: "length (tl xs) = length xs - 1"
nipkow@13145
   540
by (cases xs) auto
wenzelm@13114
   541
wenzelm@13142
   542
lemma length_0_conv [iff]: "(length xs = 0) = (xs = [])"
nipkow@13145
   543
by (induct xs) auto
wenzelm@13114
   544
wenzelm@13142
   545
lemma length_greater_0_conv [iff]: "(0 < length xs) = (xs \<noteq> [])"
nipkow@13145
   546
by (induct xs) auto
wenzelm@13114
   547
nipkow@23479
   548
lemma length_pos_if_in_set: "x : set xs \<Longrightarrow> length xs > 0"
nipkow@23479
   549
by auto
nipkow@23479
   550
wenzelm@13114
   551
lemma length_Suc_conv:
nipkow@13145
   552
"(length xs = Suc n) = (\<exists>y ys. xs = y # ys \<and> length ys = n)"
nipkow@13145
   553
by (induct xs) auto
wenzelm@13142
   554
nipkow@14025
   555
lemma Suc_length_conv:
nipkow@14025
   556
"(Suc n = length xs) = (\<exists>y ys. xs = y # ys \<and> length ys = n)"
paulson@14208
   557
apply (induct xs, simp, simp)
nipkow@14025
   558
apply blast
nipkow@14025
   559
done
nipkow@14025
   560
wenzelm@25221
   561
lemma impossible_Cons: "length xs <= length ys ==> xs = x # ys = False"
wenzelm@25221
   562
  by (induct xs) auto
wenzelm@25221
   563
haftmann@26442
   564
lemma list_induct2 [consumes 1, case_names Nil Cons]:
haftmann@26442
   565
  "length xs = length ys \<Longrightarrow> P [] [] \<Longrightarrow>
haftmann@26442
   566
   (\<And>x xs y ys. length xs = length ys \<Longrightarrow> P xs ys \<Longrightarrow> P (x#xs) (y#ys))
haftmann@26442
   567
   \<Longrightarrow> P xs ys"
haftmann@26442
   568
proof (induct xs arbitrary: ys)
haftmann@26442
   569
  case Nil then show ?case by simp
haftmann@26442
   570
next
haftmann@26442
   571
  case (Cons x xs ys) then show ?case by (cases ys) simp_all
haftmann@26442
   572
qed
haftmann@26442
   573
haftmann@26442
   574
lemma list_induct3 [consumes 2, case_names Nil Cons]:
haftmann@26442
   575
  "length xs = length ys \<Longrightarrow> length ys = length zs \<Longrightarrow> P [] [] [] \<Longrightarrow>
haftmann@26442
   576
   (\<And>x xs y ys z zs. length xs = length ys \<Longrightarrow> length ys = length zs \<Longrightarrow> P xs ys zs \<Longrightarrow> P (x#xs) (y#ys) (z#zs))
haftmann@26442
   577
   \<Longrightarrow> P xs ys zs"
haftmann@26442
   578
proof (induct xs arbitrary: ys zs)
haftmann@26442
   579
  case Nil then show ?case by simp
haftmann@26442
   580
next
haftmann@26442
   581
  case (Cons x xs ys zs) then show ?case by (cases ys, simp_all)
haftmann@26442
   582
    (cases zs, simp_all)
haftmann@26442
   583
qed
wenzelm@13114
   584
kaliszyk@36154
   585
lemma list_induct4 [consumes 3, case_names Nil Cons]:
kaliszyk@36154
   586
  "length xs = length ys \<Longrightarrow> length ys = length zs \<Longrightarrow> length zs = length ws \<Longrightarrow>
kaliszyk@36154
   587
   P [] [] [] [] \<Longrightarrow> (\<And>x xs y ys z zs w ws. length xs = length ys \<Longrightarrow>
kaliszyk@36154
   588
   length ys = length zs \<Longrightarrow> length zs = length ws \<Longrightarrow> P xs ys zs ws \<Longrightarrow>
kaliszyk@36154
   589
   P (x#xs) (y#ys) (z#zs) (w#ws)) \<Longrightarrow> P xs ys zs ws"
kaliszyk@36154
   590
proof (induct xs arbitrary: ys zs ws)
kaliszyk@36154
   591
  case Nil then show ?case by simp
kaliszyk@36154
   592
next
kaliszyk@36154
   593
  case (Cons x xs ys zs ws) then show ?case by ((cases ys, simp_all), (cases zs,simp_all)) (cases ws, simp_all)
kaliszyk@36154
   594
qed
kaliszyk@36154
   595
krauss@22493
   596
lemma list_induct2': 
krauss@22493
   597
  "\<lbrakk> P [] [];
krauss@22493
   598
  \<And>x xs. P (x#xs) [];
krauss@22493
   599
  \<And>y ys. P [] (y#ys);
krauss@22493
   600
   \<And>x xs y ys. P xs ys  \<Longrightarrow> P (x#xs) (y#ys) \<rbrakk>
krauss@22493
   601
 \<Longrightarrow> P xs ys"
krauss@22493
   602
by (induct xs arbitrary: ys) (case_tac x, auto)+
krauss@22493
   603
nipkow@22143
   604
lemma neq_if_length_neq: "length xs \<noteq> length ys \<Longrightarrow> (xs = ys) == False"
nipkow@24349
   605
by (rule Eq_FalseI) auto
wenzelm@24037
   606
wenzelm@24037
   607
simproc_setup list_neq ("(xs::'a list) = ys") = {*
nipkow@22143
   608
(*
nipkow@22143
   609
Reduces xs=ys to False if xs and ys cannot be of the same length.
nipkow@22143
   610
This is the case if the atomic sublists of one are a submultiset
nipkow@22143
   611
of those of the other list and there are fewer Cons's in one than the other.
nipkow@22143
   612
*)
wenzelm@24037
   613
wenzelm@24037
   614
let
nipkow@22143
   615
huffman@29856
   616
fun len (Const(@{const_name Nil},_)) acc = acc
huffman@29856
   617
  | len (Const(@{const_name Cons},_) $ _ $ xs) (ts,n) = len xs (ts,n+1)
huffman@29856
   618
  | len (Const(@{const_name append},_) $ xs $ ys) acc = len xs (len ys acc)
huffman@29856
   619
  | len (Const(@{const_name rev},_) $ xs) acc = len xs acc
huffman@29856
   620
  | len (Const(@{const_name map},_) $ _ $ xs) acc = len xs acc
nipkow@22143
   621
  | len t (ts,n) = (t::ts,n);
nipkow@22143
   622
wenzelm@24037
   623
fun list_neq _ ss ct =
nipkow@22143
   624
  let
wenzelm@24037
   625
    val (Const(_,eqT) $ lhs $ rhs) = Thm.term_of ct;
nipkow@22143
   626
    val (ls,m) = len lhs ([],0) and (rs,n) = len rhs ([],0);
nipkow@22143
   627
    fun prove_neq() =
nipkow@22143
   628
      let
nipkow@22143
   629
        val Type(_,listT::_) = eqT;
haftmann@22994
   630
        val size = HOLogic.size_const listT;
nipkow@22143
   631
        val eq_len = HOLogic.mk_eq (size $ lhs, size $ rhs);
nipkow@22143
   632
        val neq_len = HOLogic.mk_Trueprop (HOLogic.Not $ eq_len);
nipkow@22143
   633
        val thm = Goal.prove (Simplifier.the_context ss) [] [] neq_len
haftmann@22633
   634
          (K (simp_tac (Simplifier.inherit_context ss @{simpset}) 1));
haftmann@22633
   635
      in SOME (thm RS @{thm neq_if_length_neq}) end
nipkow@22143
   636
  in
wenzelm@23214
   637
    if m < n andalso submultiset (op aconv) (ls,rs) orelse
wenzelm@23214
   638
       n < m andalso submultiset (op aconv) (rs,ls)
nipkow@22143
   639
    then prove_neq() else NONE
nipkow@22143
   640
  end;
wenzelm@24037
   641
in list_neq end;
nipkow@22143
   642
*}
nipkow@22143
   643
nipkow@22143
   644
nipkow@15392
   645
subsubsection {* @{text "@"} -- append *}
wenzelm@13114
   646
wenzelm@13142
   647
lemma append_assoc [simp]: "(xs @ ys) @ zs = xs @ (ys @ zs)"
nipkow@13145
   648
by (induct xs) auto
wenzelm@13114
   649
wenzelm@13142
   650
lemma append_Nil2 [simp]: "xs @ [] = xs"
nipkow@13145
   651
by (induct xs) auto
nipkow@3507
   652
wenzelm@13142
   653
lemma append_is_Nil_conv [iff]: "(xs @ ys = []) = (xs = [] \<and> ys = [])"
nipkow@13145
   654
by (induct xs) auto
wenzelm@13114
   655
wenzelm@13142
   656
lemma Nil_is_append_conv [iff]: "([] = xs @ ys) = (xs = [] \<and> ys = [])"
nipkow@13145
   657
by (induct xs) auto
wenzelm@13114
   658
wenzelm@13142
   659
lemma append_self_conv [iff]: "(xs @ ys = xs) = (ys = [])"
nipkow@13145
   660
by (induct xs) auto
wenzelm@13114
   661
wenzelm@13142
   662
lemma self_append_conv [iff]: "(xs = xs @ ys) = (ys = [])"
nipkow@13145
   663
by (induct xs) auto
wenzelm@13114
   664
blanchet@35828
   665
lemma append_eq_append_conv [simp, no_atp]:
nipkow@24526
   666
 "length xs = length ys \<or> length us = length vs
berghofe@13883
   667
 ==> (xs@us = ys@vs) = (xs=ys \<and> us=vs)"
nipkow@24526
   668
apply (induct xs arbitrary: ys)
paulson@14208
   669
 apply (case_tac ys, simp, force)
paulson@14208
   670
apply (case_tac ys, force, simp)
nipkow@13145
   671
done
wenzelm@13142
   672
nipkow@24526
   673
lemma append_eq_append_conv2: "(xs @ ys = zs @ ts) =
nipkow@24526
   674
  (EX us. xs = zs @ us & us @ ys = ts | xs @ us = zs & ys = us@ ts)"
nipkow@24526
   675
apply (induct xs arbitrary: ys zs ts)
nipkow@44890
   676
 apply fastforce
nipkow@14495
   677
apply(case_tac zs)
nipkow@14495
   678
 apply simp
nipkow@44890
   679
apply fastforce
nipkow@14495
   680
done
nipkow@14495
   681
berghofe@34910
   682
lemma same_append_eq [iff, induct_simp]: "(xs @ ys = xs @ zs) = (ys = zs)"
nipkow@13145
   683
by simp
wenzelm@13142
   684
wenzelm@13142
   685
lemma append1_eq_conv [iff]: "(xs @ [x] = ys @ [y]) = (xs = ys \<and> x = y)"
nipkow@13145
   686
by simp
wenzelm@13114
   687
berghofe@34910
   688
lemma append_same_eq [iff, induct_simp]: "(ys @ xs = zs @ xs) = (ys = zs)"
nipkow@13145
   689
by simp
wenzelm@13114
   690
wenzelm@13142
   691
lemma append_self_conv2 [iff]: "(xs @ ys = ys) = (xs = [])"
nipkow@13145
   692
using append_same_eq [of _ _ "[]"] by auto
nipkow@3507
   693
wenzelm@13142
   694
lemma self_append_conv2 [iff]: "(ys = xs @ ys) = (xs = [])"
nipkow@13145
   695
using append_same_eq [of "[]"] by auto
wenzelm@13114
   696
blanchet@35828
   697
lemma hd_Cons_tl [simp,no_atp]: "xs \<noteq> [] ==> hd xs # tl xs = xs"
nipkow@13145
   698
by (induct xs) auto
wenzelm@13114
   699
wenzelm@13142
   700
lemma hd_append: "hd (xs @ ys) = (if xs = [] then hd ys else hd xs)"
nipkow@13145
   701
by (induct xs) auto
wenzelm@13114
   702
wenzelm@13142
   703
lemma hd_append2 [simp]: "xs \<noteq> [] ==> hd (xs @ ys) = hd xs"
nipkow@13145
   704
by (simp add: hd_append split: list.split)
wenzelm@13114
   705
wenzelm@13142
   706
lemma tl_append: "tl (xs @ ys) = (case xs of [] => tl ys | z#zs => zs @ ys)"
nipkow@13145
   707
by (simp split: list.split)
wenzelm@13114
   708
wenzelm@13142
   709
lemma tl_append2 [simp]: "xs \<noteq> [] ==> tl (xs @ ys) = tl xs @ ys"
nipkow@13145
   710
by (simp add: tl_append split: list.split)
wenzelm@13114
   711
wenzelm@13114
   712
nipkow@14300
   713
lemma Cons_eq_append_conv: "x#xs = ys@zs =
nipkow@14300
   714
 (ys = [] & x#xs = zs | (EX ys'. x#ys' = ys & xs = ys'@zs))"
nipkow@14300
   715
by(cases ys) auto
nipkow@14300
   716
nipkow@15281
   717
lemma append_eq_Cons_conv: "(ys@zs = x#xs) =
nipkow@15281
   718
 (ys = [] & zs = x#xs | (EX ys'. ys = x#ys' & ys'@zs = xs))"
nipkow@15281
   719
by(cases ys) auto
nipkow@15281
   720
nipkow@14300
   721
wenzelm@13142
   722
text {* Trivial rules for solving @{text "@"}-equations automatically. *}
wenzelm@13114
   723
wenzelm@13114
   724
lemma eq_Nil_appendI: "xs = ys ==> xs = [] @ ys"
nipkow@13145
   725
by simp
wenzelm@13114
   726
wenzelm@13142
   727
lemma Cons_eq_appendI:
nipkow@13145
   728
"[| x # xs1 = ys; xs = xs1 @ zs |] ==> x # xs = ys @ zs"
nipkow@13145
   729
by (drule sym) simp
wenzelm@13114
   730
wenzelm@13142
   731
lemma append_eq_appendI:
nipkow@13145
   732
"[| xs @ xs1 = zs; ys = xs1 @ us |] ==> xs @ ys = zs @ us"
nipkow@13145
   733
by (drule sym) simp
wenzelm@13114
   734
wenzelm@13114
   735
wenzelm@13142
   736
text {*
nipkow@13145
   737
Simplification procedure for all list equalities.
nipkow@13145
   738
Currently only tries to rearrange @{text "@"} to see if
nipkow@13145
   739
- both lists end in a singleton list,
nipkow@13145
   740
- or both lists end in the same list.
wenzelm@13142
   741
*}
wenzelm@13142
   742
wenzelm@43594
   743
simproc_setup list_eq ("(xs::'a list) = ys")  = {*
wenzelm@13462
   744
  let
wenzelm@43594
   745
    fun last (cons as Const (@{const_name Cons}, _) $ _ $ xs) =
wenzelm@43594
   746
          (case xs of Const (@{const_name Nil}, _) => cons | _ => last xs)
wenzelm@43594
   747
      | last (Const(@{const_name append},_) $ _ $ ys) = last ys
wenzelm@43594
   748
      | last t = t;
wenzelm@43594
   749
    
wenzelm@43594
   750
    fun list1 (Const(@{const_name Cons},_) $ _ $ Const(@{const_name Nil},_)) = true
wenzelm@43594
   751
      | list1 _ = false;
wenzelm@43594
   752
    
wenzelm@43594
   753
    fun butlast ((cons as Const(@{const_name Cons},_) $ x) $ xs) =
wenzelm@43594
   754
          (case xs of Const (@{const_name Nil}, _) => xs | _ => cons $ butlast xs)
wenzelm@43594
   755
      | butlast ((app as Const (@{const_name append}, _) $ xs) $ ys) = app $ butlast ys
wenzelm@43594
   756
      | butlast xs = Const(@{const_name Nil}, fastype_of xs);
wenzelm@43594
   757
    
wenzelm@43594
   758
    val rearr_ss =
wenzelm@43594
   759
      HOL_basic_ss addsimps [@{thm append_assoc}, @{thm append_Nil}, @{thm append_Cons}];
wenzelm@43594
   760
    
wenzelm@43594
   761
    fun list_eq ss (F as (eq as Const(_,eqT)) $ lhs $ rhs) =
wenzelm@13462
   762
      let
wenzelm@43594
   763
        val lastl = last lhs and lastr = last rhs;
wenzelm@43594
   764
        fun rearr conv =
wenzelm@43594
   765
          let
wenzelm@43594
   766
            val lhs1 = butlast lhs and rhs1 = butlast rhs;
wenzelm@43594
   767
            val Type(_,listT::_) = eqT
wenzelm@43594
   768
            val appT = [listT,listT] ---> listT
wenzelm@43594
   769
            val app = Const(@{const_name append},appT)
wenzelm@43594
   770
            val F2 = eq $ (app$lhs1$lastl) $ (app$rhs1$lastr)
wenzelm@43594
   771
            val eq = HOLogic.mk_Trueprop (HOLogic.mk_eq (F,F2));
wenzelm@43594
   772
            val thm = Goal.prove (Simplifier.the_context ss) [] [] eq
wenzelm@43594
   773
              (K (simp_tac (Simplifier.inherit_context ss rearr_ss) 1));
wenzelm@43594
   774
          in SOME ((conv RS (thm RS trans)) RS eq_reflection) end;
wenzelm@43594
   775
      in
wenzelm@43594
   776
        if list1 lastl andalso list1 lastr then rearr @{thm append1_eq_conv}
wenzelm@43594
   777
        else if lastl aconv lastr then rearr @{thm append_same_eq}
wenzelm@43594
   778
        else NONE
wenzelm@43594
   779
      end;
wenzelm@43594
   780
  in fn _ => fn ss => fn ct => list_eq ss (term_of ct) end;
wenzelm@13114
   781
*}
wenzelm@13114
   782
wenzelm@13114
   783
nipkow@15392
   784
subsubsection {* @{text map} *}
wenzelm@13114
   785
haftmann@40210
   786
lemma hd_map:
haftmann@40210
   787
  "xs \<noteq> [] \<Longrightarrow> hd (map f xs) = f (hd xs)"
haftmann@40210
   788
  by (cases xs) simp_all
haftmann@40210
   789
haftmann@40210
   790
lemma map_tl:
haftmann@40210
   791
  "map f (tl xs) = tl (map f xs)"
haftmann@40210
   792
  by (cases xs) simp_all
haftmann@40210
   793
wenzelm@13142
   794
lemma map_ext: "(!!x. x : set xs --> f x = g x) ==> map f xs = map g xs"
nipkow@13145
   795
by (induct xs) simp_all
wenzelm@13114
   796
wenzelm@13142
   797
lemma map_ident [simp]: "map (\<lambda>x. x) = (\<lambda>xs. xs)"
nipkow@13145
   798
by (rule ext, induct_tac xs) auto
wenzelm@13114
   799
wenzelm@13142
   800
lemma map_append [simp]: "map f (xs @ ys) = map f xs @ map f ys"
nipkow@13145
   801
by (induct xs) auto
wenzelm@13114
   802
hoelzl@33639
   803
lemma map_map [simp]: "map f (map g xs) = map (f \<circ> g) xs"
hoelzl@33639
   804
by (induct xs) auto
hoelzl@33639
   805
nipkow@35208
   806
lemma map_comp_map[simp]: "((map f) o (map g)) = map(f o g)"
nipkow@35208
   807
apply(rule ext)
nipkow@35208
   808
apply(simp)
nipkow@35208
   809
done
nipkow@35208
   810
wenzelm@13142
   811
lemma rev_map: "rev (map f xs) = map f (rev xs)"
nipkow@13145
   812
by (induct xs) auto
wenzelm@13114
   813
nipkow@13737
   814
lemma map_eq_conv[simp]: "(map f xs = map g xs) = (!x : set xs. f x = g x)"
nipkow@13737
   815
by (induct xs) auto
nipkow@13737
   816
krauss@44013
   817
lemma map_cong [fundef_cong]:
haftmann@40122
   818
  "xs = ys \<Longrightarrow> (\<And>x. x \<in> set ys \<Longrightarrow> f x = g x) \<Longrightarrow> map f xs = map g ys"
haftmann@40122
   819
  by simp
wenzelm@13114
   820
wenzelm@13142
   821
lemma map_is_Nil_conv [iff]: "(map f xs = []) = (xs = [])"
nipkow@13145
   822
by (cases xs) auto
wenzelm@13114
   823
wenzelm@13142
   824
lemma Nil_is_map_conv [iff]: "([] = map f xs) = (xs = [])"
nipkow@13145
   825
by (cases xs) auto
wenzelm@13114
   826
paulson@18447
   827
lemma map_eq_Cons_conv:
nipkow@14025
   828
 "(map f xs = y#ys) = (\<exists>z zs. xs = z#zs \<and> f z = y \<and> map f zs = ys)"
nipkow@13145
   829
by (cases xs) auto
wenzelm@13114
   830
paulson@18447
   831
lemma Cons_eq_map_conv:
nipkow@14025
   832
 "(x#xs = map f ys) = (\<exists>z zs. ys = z#zs \<and> x = f z \<and> xs = map f zs)"
nipkow@14025
   833
by (cases ys) auto
nipkow@14025
   834
paulson@18447
   835
lemmas map_eq_Cons_D = map_eq_Cons_conv [THEN iffD1]
paulson@18447
   836
lemmas Cons_eq_map_D = Cons_eq_map_conv [THEN iffD1]
paulson@18447
   837
declare map_eq_Cons_D [dest!]  Cons_eq_map_D [dest!]
paulson@18447
   838
nipkow@14111
   839
lemma ex_map_conv:
nipkow@14111
   840
  "(EX xs. ys = map f xs) = (ALL y : set ys. EX x. y = f x)"
paulson@18447
   841
by(induct ys, auto simp add: Cons_eq_map_conv)
nipkow@14111
   842
nipkow@15110
   843
lemma map_eq_imp_length_eq:
paulson@35510
   844
  assumes "map f xs = map g ys"
haftmann@26734
   845
  shows "length xs = length ys"
haftmann@26734
   846
using assms proof (induct ys arbitrary: xs)
haftmann@26734
   847
  case Nil then show ?case by simp
haftmann@26734
   848
next
haftmann@26734
   849
  case (Cons y ys) then obtain z zs where xs: "xs = z # zs" by auto
paulson@35510
   850
  from Cons xs have "map f zs = map g ys" by simp
haftmann@26734
   851
  moreover with Cons have "length zs = length ys" by blast
haftmann@26734
   852
  with xs show ?case by simp
haftmann@26734
   853
qed
haftmann@26734
   854
  
nipkow@15110
   855
lemma map_inj_on:
nipkow@15110
   856
 "[| map f xs = map f ys; inj_on f (set xs Un set ys) |]
nipkow@15110
   857
  ==> xs = ys"
nipkow@15110
   858
apply(frule map_eq_imp_length_eq)
nipkow@15110
   859
apply(rotate_tac -1)
nipkow@15110
   860
apply(induct rule:list_induct2)
nipkow@15110
   861
 apply simp
nipkow@15110
   862
apply(simp)
nipkow@15110
   863
apply (blast intro:sym)
nipkow@15110
   864
done
nipkow@15110
   865
nipkow@15110
   866
lemma inj_on_map_eq_map:
nipkow@15110
   867
 "inj_on f (set xs Un set ys) \<Longrightarrow> (map f xs = map f ys) = (xs = ys)"
nipkow@15110
   868
by(blast dest:map_inj_on)
nipkow@15110
   869
wenzelm@13114
   870
lemma map_injective:
nipkow@24526
   871
 "map f xs = map f ys ==> inj f ==> xs = ys"
nipkow@24526
   872
by (induct ys arbitrary: xs) (auto dest!:injD)
wenzelm@13114
   873
nipkow@14339
   874
lemma inj_map_eq_map[simp]: "inj f \<Longrightarrow> (map f xs = map f ys) = (xs = ys)"
nipkow@14339
   875
by(blast dest:map_injective)
nipkow@14339
   876
wenzelm@13114
   877
lemma inj_mapI: "inj f ==> inj (map f)"
nipkow@17589
   878
by (iprover dest: map_injective injD intro: inj_onI)
wenzelm@13114
   879
wenzelm@13114
   880
lemma inj_mapD: "inj (map f) ==> inj f"
paulson@14208
   881
apply (unfold inj_on_def, clarify)
nipkow@13145
   882
apply (erule_tac x = "[x]" in ballE)
paulson@14208
   883
 apply (erule_tac x = "[y]" in ballE, simp, blast)
nipkow@13145
   884
apply blast
nipkow@13145
   885
done
wenzelm@13114
   886
nipkow@14339
   887
lemma inj_map[iff]: "inj (map f) = inj f"
nipkow@13145
   888
by (blast dest: inj_mapD intro: inj_mapI)
wenzelm@13114
   889
nipkow@15303
   890
lemma inj_on_mapI: "inj_on f (\<Union>(set ` A)) \<Longrightarrow> inj_on (map f) A"
nipkow@15303
   891
apply(rule inj_onI)
nipkow@15303
   892
apply(erule map_inj_on)
nipkow@15303
   893
apply(blast intro:inj_onI dest:inj_onD)
nipkow@15303
   894
done
nipkow@15303
   895
kleing@14343
   896
lemma map_idI: "(\<And>x. x \<in> set xs \<Longrightarrow> f x = x) \<Longrightarrow> map f xs = xs"
kleing@14343
   897
by (induct xs, auto)
wenzelm@13114
   898
nipkow@14402
   899
lemma map_fun_upd [simp]: "y \<notin> set xs \<Longrightarrow> map (f(y:=v)) xs = map f xs"
nipkow@14402
   900
by (induct xs) auto
nipkow@14402
   901
nipkow@15110
   902
lemma map_fst_zip[simp]:
nipkow@15110
   903
  "length xs = length ys \<Longrightarrow> map fst (zip xs ys) = xs"
nipkow@15110
   904
by (induct rule:list_induct2, simp_all)
nipkow@15110
   905
nipkow@15110
   906
lemma map_snd_zip[simp]:
nipkow@15110
   907
  "length xs = length ys \<Longrightarrow> map snd (zip xs ys) = ys"
nipkow@15110
   908
by (induct rule:list_induct2, simp_all)
nipkow@15110
   909
haftmann@41505
   910
enriched_type map: map
haftmann@41372
   911
  by (simp_all add: fun_eq_iff id_def)
haftmann@40608
   912
nipkow@15110
   913
nipkow@15392
   914
subsubsection {* @{text rev} *}
wenzelm@13114
   915
wenzelm@13142
   916
lemma rev_append [simp]: "rev (xs @ ys) = rev ys @ rev xs"
nipkow@13145
   917
by (induct xs) auto
wenzelm@13114
   918
wenzelm@13142
   919
lemma rev_rev_ident [simp]: "rev (rev xs) = xs"
nipkow@13145
   920
by (induct xs) auto
wenzelm@13114
   921
kleing@15870
   922
lemma rev_swap: "(rev xs = ys) = (xs = rev ys)"
kleing@15870
   923
by auto
kleing@15870
   924
wenzelm@13142
   925
lemma rev_is_Nil_conv [iff]: "(rev xs = []) = (xs = [])"
nipkow@13145
   926
by (induct xs) auto
wenzelm@13114
   927
wenzelm@13142
   928
lemma Nil_is_rev_conv [iff]: "([] = rev xs) = (xs = [])"
nipkow@13145
   929
by (induct xs) auto
wenzelm@13114
   930
kleing@15870
   931
lemma rev_singleton_conv [simp]: "(rev xs = [x]) = (xs = [x])"
kleing@15870
   932
by (cases xs) auto
kleing@15870
   933
kleing@15870
   934
lemma singleton_rev_conv [simp]: "([x] = rev xs) = (xs = [x])"
kleing@15870
   935
by (cases xs) auto
kleing@15870
   936
blanchet@46439
   937
lemma rev_is_rev_conv [iff, no_atp]: "(rev xs = rev ys) = (xs = ys)"
haftmann@21061
   938
apply (induct xs arbitrary: ys, force)
paulson@14208
   939
apply (case_tac ys, simp, force)
nipkow@13145
   940
done
wenzelm@13114
   941
nipkow@15439
   942
lemma inj_on_rev[iff]: "inj_on rev A"
nipkow@15439
   943
by(simp add:inj_on_def)
nipkow@15439
   944
wenzelm@13366
   945
lemma rev_induct [case_names Nil snoc]:
wenzelm@13366
   946
  "[| P []; !!x xs. P xs ==> P (xs @ [x]) |] ==> P xs"
berghofe@15489
   947
apply(simplesubst rev_rev_ident[symmetric])
nipkow@13145
   948
apply(rule_tac list = "rev xs" in list.induct, simp_all)
nipkow@13145
   949
done
wenzelm@13114
   950
wenzelm@13366
   951
lemma rev_exhaust [case_names Nil snoc]:
wenzelm@13366
   952
  "(xs = [] ==> P) ==>(!!ys y. xs = ys @ [y] ==> P) ==> P"
nipkow@13145
   953
by (induct xs rule: rev_induct) auto
wenzelm@13114
   954
wenzelm@13366
   955
lemmas rev_cases = rev_exhaust
wenzelm@13366
   956
nipkow@18423
   957
lemma rev_eq_Cons_iff[iff]: "(rev xs = y#ys) = (xs = rev ys @ [y])"
nipkow@18423
   958
by(rule rev_cases[of xs]) auto
nipkow@18423
   959
wenzelm@13114
   960
nipkow@15392
   961
subsubsection {* @{text set} *}
wenzelm@13114
   962
nipkow@46698
   963
declare set.simps [code_post]  --"pretty output"
nipkow@46698
   964
wenzelm@13142
   965
lemma finite_set [iff]: "finite (set xs)"
nipkow@13145
   966
by (induct xs) auto
wenzelm@13114
   967
wenzelm@13142
   968
lemma set_append [simp]: "set (xs @ ys) = (set xs \<union> set ys)"
nipkow@13145
   969
by (induct xs) auto
wenzelm@13114
   970
nipkow@17830
   971
lemma hd_in_set[simp]: "xs \<noteq> [] \<Longrightarrow> hd xs : set xs"
nipkow@17830
   972
by(cases xs) auto
oheimb@14099
   973
wenzelm@13142
   974
lemma set_subset_Cons: "set xs \<subseteq> set (x # xs)"
nipkow@13145
   975
by auto
wenzelm@13114
   976
oheimb@14099
   977
lemma set_ConsD: "y \<in> set (x # xs) \<Longrightarrow> y=x \<or> y \<in> set xs" 
oheimb@14099
   978
by auto
oheimb@14099
   979
wenzelm@13142
   980
lemma set_empty [iff]: "(set xs = {}) = (xs = [])"
nipkow@13145
   981
by (induct xs) auto
wenzelm@13114
   982
nipkow@15245
   983
lemma set_empty2[iff]: "({} = set xs) = (xs = [])"
nipkow@15245
   984
by(induct xs) auto
nipkow@15245
   985
wenzelm@13142
   986
lemma set_rev [simp]: "set (rev xs) = set xs"
nipkow@13145
   987
by (induct xs) auto
wenzelm@13114
   988
wenzelm@13142
   989
lemma set_map [simp]: "set (map f xs) = f`(set xs)"
nipkow@13145
   990
by (induct xs) auto
wenzelm@13114
   991
wenzelm@13142
   992
lemma set_filter [simp]: "set (filter P xs) = {x. x : set xs \<and> P x}"
nipkow@13145
   993
by (induct xs) auto
wenzelm@13114
   994
nipkow@32417
   995
lemma set_upt [simp]: "set[i..<j] = {i..<j}"
bulwahn@41463
   996
by (induct j) auto
wenzelm@13114
   997
wenzelm@13142
   998
wenzelm@25221
   999
lemma split_list: "x : set xs \<Longrightarrow> \<exists>ys zs. xs = ys @ x # zs"
nipkow@18049
  1000
proof (induct xs)
nipkow@26073
  1001
  case Nil thus ?case by simp
nipkow@26073
  1002
next
nipkow@26073
  1003
  case Cons thus ?case by (auto intro: Cons_eq_appendI)
nipkow@26073
  1004
qed
nipkow@26073
  1005
haftmann@26734
  1006
lemma in_set_conv_decomp: "x \<in> set xs \<longleftrightarrow> (\<exists>ys zs. xs = ys @ x # zs)"
haftmann@26734
  1007
  by (auto elim: split_list)
nipkow@26073
  1008
nipkow@26073
  1009
lemma split_list_first: "x : set xs \<Longrightarrow> \<exists>ys zs. xs = ys @ x # zs \<and> x \<notin> set ys"
nipkow@26073
  1010
proof (induct xs)
nipkow@26073
  1011
  case Nil thus ?case by simp
nipkow@18049
  1012
next
nipkow@18049
  1013
  case (Cons a xs)
nipkow@18049
  1014
  show ?case
nipkow@18049
  1015
  proof cases
nipkow@44890
  1016
    assume "x = a" thus ?case using Cons by fastforce
nipkow@18049
  1017
  next
nipkow@44890
  1018
    assume "x \<noteq> a" thus ?case using Cons by(fastforce intro!: Cons_eq_appendI)
nipkow@26073
  1019
  qed
nipkow@26073
  1020
qed
nipkow@26073
  1021
nipkow@26073
  1022
lemma in_set_conv_decomp_first:
nipkow@26073
  1023
  "(x : set xs) = (\<exists>ys zs. xs = ys @ x # zs \<and> x \<notin> set ys)"
haftmann@26734
  1024
  by (auto dest!: split_list_first)
nipkow@26073
  1025
haftmann@40122
  1026
lemma split_list_last: "x \<in> set xs \<Longrightarrow> \<exists>ys zs. xs = ys @ x # zs \<and> x \<notin> set zs"
haftmann@40122
  1027
proof (induct xs rule: rev_induct)
nipkow@26073
  1028
  case Nil thus ?case by simp
nipkow@26073
  1029
next
nipkow@26073
  1030
  case (snoc a xs)
nipkow@26073
  1031
  show ?case
nipkow@26073
  1032
  proof cases
haftmann@40122
  1033
    assume "x = a" thus ?case using snoc by (metis List.set.simps(1) emptyE)
nipkow@26073
  1034
  next
nipkow@44890
  1035
    assume "x \<noteq> a" thus ?case using snoc by fastforce
nipkow@18049
  1036
  qed
nipkow@18049
  1037
qed
nipkow@18049
  1038
nipkow@26073
  1039
lemma in_set_conv_decomp_last:
nipkow@26073
  1040
  "(x : set xs) = (\<exists>ys zs. xs = ys @ x # zs \<and> x \<notin> set zs)"
haftmann@26734
  1041
  by (auto dest!: split_list_last)
nipkow@26073
  1042
nipkow@26073
  1043
lemma split_list_prop: "\<exists>x \<in> set xs. P x \<Longrightarrow> \<exists>ys x zs. xs = ys @ x # zs & P x"
nipkow@26073
  1044
proof (induct xs)
nipkow@26073
  1045
  case Nil thus ?case by simp
nipkow@26073
  1046
next
nipkow@26073
  1047
  case Cons thus ?case
nipkow@26073
  1048
    by(simp add:Bex_def)(metis append_Cons append.simps(1))
nipkow@26073
  1049
qed
nipkow@26073
  1050
nipkow@26073
  1051
lemma split_list_propE:
haftmann@26734
  1052
  assumes "\<exists>x \<in> set xs. P x"
haftmann@26734
  1053
  obtains ys x zs where "xs = ys @ x # zs" and "P x"
haftmann@26734
  1054
using split_list_prop [OF assms] by blast
nipkow@26073
  1055
nipkow@26073
  1056
lemma split_list_first_prop:
nipkow@26073
  1057
  "\<exists>x \<in> set xs. P x \<Longrightarrow>
nipkow@26073
  1058
   \<exists>ys x zs. xs = ys@x#zs \<and> P x \<and> (\<forall>y \<in> set ys. \<not> P y)"
haftmann@26734
  1059
proof (induct xs)
nipkow@26073
  1060
  case Nil thus ?case by simp
nipkow@26073
  1061
next
nipkow@26073
  1062
  case (Cons x xs)
nipkow@26073
  1063
  show ?case
nipkow@26073
  1064
  proof cases
nipkow@26073
  1065
    assume "P x"
haftmann@40122
  1066
    thus ?thesis by simp (metis Un_upper1 contra_subsetD in_set_conv_decomp_first self_append_conv2 set_append)
nipkow@26073
  1067
  next
nipkow@26073
  1068
    assume "\<not> P x"
nipkow@26073
  1069
    hence "\<exists>x\<in>set xs. P x" using Cons(2) by simp
nipkow@26073
  1070
    thus ?thesis using `\<not> P x` Cons(1) by (metis append_Cons set_ConsD)
nipkow@26073
  1071
  qed
nipkow@26073
  1072
qed
nipkow@26073
  1073
nipkow@26073
  1074
lemma split_list_first_propE:
haftmann@26734
  1075
  assumes "\<exists>x \<in> set xs. P x"
haftmann@26734
  1076
  obtains ys x zs where "xs = ys @ x # zs" and "P x" and "\<forall>y \<in> set ys. \<not> P y"
haftmann@26734
  1077
using split_list_first_prop [OF assms] by blast
nipkow@26073
  1078
nipkow@26073
  1079
lemma split_list_first_prop_iff:
nipkow@26073
  1080
  "(\<exists>x \<in> set xs. P x) \<longleftrightarrow>
nipkow@26073
  1081
   (\<exists>ys x zs. xs = ys@x#zs \<and> P x \<and> (\<forall>y \<in> set ys. \<not> P y))"
haftmann@26734
  1082
by (rule, erule split_list_first_prop) auto
nipkow@26073
  1083
nipkow@26073
  1084
lemma split_list_last_prop:
nipkow@26073
  1085
  "\<exists>x \<in> set xs. P x \<Longrightarrow>
nipkow@26073
  1086
   \<exists>ys x zs. xs = ys@x#zs \<and> P x \<and> (\<forall>z \<in> set zs. \<not> P z)"
nipkow@26073
  1087
proof(induct xs rule:rev_induct)
nipkow@26073
  1088
  case Nil thus ?case by simp
nipkow@26073
  1089
next
nipkow@26073
  1090
  case (snoc x xs)
nipkow@26073
  1091
  show ?case
nipkow@26073
  1092
  proof cases
nipkow@26073
  1093
    assume "P x" thus ?thesis by (metis emptyE set_empty)
nipkow@26073
  1094
  next
nipkow@26073
  1095
    assume "\<not> P x"
nipkow@26073
  1096
    hence "\<exists>x\<in>set xs. P x" using snoc(2) by simp
nipkow@44890
  1097
    thus ?thesis using `\<not> P x` snoc(1) by fastforce
nipkow@26073
  1098
  qed
nipkow@26073
  1099
qed
nipkow@26073
  1100
nipkow@26073
  1101
lemma split_list_last_propE:
haftmann@26734
  1102
  assumes "\<exists>x \<in> set xs. P x"
haftmann@26734
  1103
  obtains ys x zs where "xs = ys @ x # zs" and "P x" and "\<forall>z \<in> set zs. \<not> P z"
haftmann@26734
  1104
using split_list_last_prop [OF assms] by blast
nipkow@26073
  1105
nipkow@26073
  1106
lemma split_list_last_prop_iff:
nipkow@26073
  1107
  "(\<exists>x \<in> set xs. P x) \<longleftrightarrow>
nipkow@26073
  1108
   (\<exists>ys x zs. xs = ys@x#zs \<and> P x \<and> (\<forall>z \<in> set zs. \<not> P z))"
haftmann@26734
  1109
by (metis split_list_last_prop [where P=P] in_set_conv_decomp)
nipkow@26073
  1110
nipkow@26073
  1111
lemma finite_list: "finite A ==> EX xs. set xs = A"
haftmann@26734
  1112
  by (erule finite_induct)
haftmann@26734
  1113
    (auto simp add: set.simps(2) [symmetric] simp del: set.simps(2))
paulson@13508
  1114
kleing@14388
  1115
lemma card_length: "card (set xs) \<le> length xs"
kleing@14388
  1116
by (induct xs) (auto simp add: card_insert_if)
wenzelm@13114
  1117
haftmann@26442
  1118
lemma set_minus_filter_out:
haftmann@26442
  1119
  "set xs - {y} = set (filter (\<lambda>x. \<not> (x = y)) xs)"
haftmann@26442
  1120
  by (induct xs) auto
paulson@15168
  1121
wenzelm@35115
  1122
nipkow@15392
  1123
subsubsection {* @{text filter} *}
wenzelm@13114
  1124
wenzelm@13142
  1125
lemma filter_append [simp]: "filter P (xs @ ys) = filter P xs @ filter P ys"
nipkow@13145
  1126
by (induct xs) auto
wenzelm@13114
  1127
nipkow@15305
  1128
lemma rev_filter: "rev (filter P xs) = filter P (rev xs)"
nipkow@15305
  1129
by (induct xs) simp_all
nipkow@15305
  1130
wenzelm@13142
  1131
lemma filter_filter [simp]: "filter P (filter Q xs) = filter (\<lambda>x. Q x \<and> P x) xs"
nipkow@13145
  1132
by (induct xs) auto
wenzelm@13114
  1133
nipkow@16998
  1134
lemma length_filter_le [simp]: "length (filter P xs) \<le> length xs"
nipkow@16998
  1135
by (induct xs) (auto simp add: le_SucI)
nipkow@16998
  1136
nipkow@18423
  1137
lemma sum_length_filter_compl:
nipkow@18423
  1138
  "length(filter P xs) + length(filter (%x. ~P x) xs) = length xs"
nipkow@18423
  1139
by(induct xs) simp_all
nipkow@18423
  1140
wenzelm@13142
  1141
lemma filter_True [simp]: "\<forall>x \<in> set xs. P x ==> filter P xs = xs"
nipkow@13145
  1142
by (induct xs) auto
wenzelm@13114
  1143
wenzelm@13142
  1144
lemma filter_False [simp]: "\<forall>x \<in> set xs. \<not> P x ==> filter P xs = []"
nipkow@13145
  1145
by (induct xs) auto
wenzelm@13114
  1146
nipkow@16998
  1147
lemma filter_empty_conv: "(filter P xs = []) = (\<forall>x\<in>set xs. \<not> P x)" 
nipkow@24349
  1148
by (induct xs) simp_all
nipkow@16998
  1149
nipkow@16998
  1150
lemma filter_id_conv: "(filter P xs = xs) = (\<forall>x\<in>set xs. P x)"
nipkow@16998
  1151
apply (induct xs)
nipkow@16998
  1152
 apply auto
nipkow@16998
  1153
apply(cut_tac P=P and xs=xs in length_filter_le)
nipkow@16998
  1154
apply simp
nipkow@16998
  1155
done
wenzelm@13114
  1156
nipkow@16965
  1157
lemma filter_map:
nipkow@16965
  1158
  "filter P (map f xs) = map f (filter (P o f) xs)"
nipkow@16965
  1159
by (induct xs) simp_all
nipkow@16965
  1160
nipkow@16965
  1161
lemma length_filter_map[simp]:
nipkow@16965
  1162
  "length (filter P (map f xs)) = length(filter (P o f) xs)"
nipkow@16965
  1163
by (simp add:filter_map)
nipkow@16965
  1164
wenzelm@13142
  1165
lemma filter_is_subset [simp]: "set (filter P xs) \<le> set xs"
nipkow@13145
  1166
by auto
wenzelm@13114
  1167
nipkow@15246
  1168
lemma length_filter_less:
nipkow@15246
  1169
  "\<lbrakk> x : set xs; ~ P x \<rbrakk> \<Longrightarrow> length(filter P xs) < length xs"
nipkow@15246
  1170
proof (induct xs)
nipkow@15246
  1171
  case Nil thus ?case by simp
nipkow@15246
  1172
next
nipkow@15246
  1173
  case (Cons x xs) thus ?case
nipkow@15246
  1174
    apply (auto split:split_if_asm)
nipkow@15246
  1175
    using length_filter_le[of P xs] apply arith
nipkow@15246
  1176
  done
nipkow@15246
  1177
qed
wenzelm@13114
  1178
nipkow@15281
  1179
lemma length_filter_conv_card:
nipkow@15281
  1180
 "length(filter p xs) = card{i. i < length xs & p(xs!i)}"
nipkow@15281
  1181
proof (induct xs)
nipkow@15281
  1182
  case Nil thus ?case by simp
nipkow@15281
  1183
next
nipkow@15281
  1184
  case (Cons x xs)
nipkow@15281
  1185
  let ?S = "{i. i < length xs & p(xs!i)}"
nipkow@15281
  1186
  have fin: "finite ?S" by(fast intro: bounded_nat_set_is_finite)
nipkow@15281
  1187
  show ?case (is "?l = card ?S'")
nipkow@15281
  1188
  proof (cases)
nipkow@15281
  1189
    assume "p x"
nipkow@15281
  1190
    hence eq: "?S' = insert 0 (Suc ` ?S)"
nipkow@25162
  1191
      by(auto simp: image_def split:nat.split dest:gr0_implies_Suc)
nipkow@15281
  1192
    have "length (filter p (x # xs)) = Suc(card ?S)"
wenzelm@23388
  1193
      using Cons `p x` by simp
nipkow@15281
  1194
    also have "\<dots> = Suc(card(Suc ` ?S))" using fin
huffman@44921
  1195
      by (simp add: card_image)
nipkow@15281
  1196
    also have "\<dots> = card ?S'" using eq fin
nipkow@15281
  1197
      by (simp add:card_insert_if) (simp add:image_def)
nipkow@15281
  1198
    finally show ?thesis .
nipkow@15281
  1199
  next
nipkow@15281
  1200
    assume "\<not> p x"
nipkow@15281
  1201
    hence eq: "?S' = Suc ` ?S"
nipkow@25162
  1202
      by(auto simp add: image_def split:nat.split elim:lessE)
nipkow@15281
  1203
    have "length (filter p (x # xs)) = card ?S"
wenzelm@23388
  1204
      using Cons `\<not> p x` by simp
nipkow@15281
  1205
    also have "\<dots> = card(Suc ` ?S)" using fin
huffman@44921
  1206
      by (simp add: card_image)
nipkow@15281
  1207
    also have "\<dots> = card ?S'" using eq fin
nipkow@15281
  1208
      by (simp add:card_insert_if)
nipkow@15281
  1209
    finally show ?thesis .
nipkow@15281
  1210
  qed
nipkow@15281
  1211
qed
nipkow@15281
  1212
nipkow@17629
  1213
lemma Cons_eq_filterD:
nipkow@17629
  1214
 "x#xs = filter P ys \<Longrightarrow>
nipkow@17629
  1215
  \<exists>us vs. ys = us @ x # vs \<and> (\<forall>u\<in>set us. \<not> P u) \<and> P x \<and> xs = filter P vs"
wenzelm@19585
  1216
  (is "_ \<Longrightarrow> \<exists>us vs. ?P ys us vs")
nipkow@17629
  1217
proof(induct ys)
nipkow@17629
  1218
  case Nil thus ?case by simp
nipkow@17629
  1219
next
nipkow@17629
  1220
  case (Cons y ys)
nipkow@17629
  1221
  show ?case (is "\<exists>x. ?Q x")
nipkow@17629
  1222
  proof cases
nipkow@17629
  1223
    assume Py: "P y"
nipkow@17629
  1224
    show ?thesis
nipkow@17629
  1225
    proof cases
wenzelm@25221
  1226
      assume "x = y"
wenzelm@25221
  1227
      with Py Cons.prems have "?Q []" by simp
wenzelm@25221
  1228
      then show ?thesis ..
nipkow@17629
  1229
    next
wenzelm@25221
  1230
      assume "x \<noteq> y"
wenzelm@25221
  1231
      with Py Cons.prems show ?thesis by simp
nipkow@17629
  1232
    qed
nipkow@17629
  1233
  next
wenzelm@25221
  1234
    assume "\<not> P y"
nipkow@44890
  1235
    with Cons obtain us vs where "?P (y#ys) (y#us) vs" by fastforce
wenzelm@25221
  1236
    then have "?Q (y#us)" by simp
wenzelm@25221
  1237
    then show ?thesis ..
nipkow@17629
  1238
  qed
nipkow@17629
  1239
qed
nipkow@17629
  1240
nipkow@17629
  1241
lemma filter_eq_ConsD:
nipkow@17629
  1242
 "filter P ys = x#xs \<Longrightarrow>
nipkow@17629
  1243
  \<exists>us vs. ys = us @ x # vs \<and> (\<forall>u\<in>set us. \<not> P u) \<and> P x \<and> xs = filter P vs"
nipkow@17629
  1244
by(rule Cons_eq_filterD) simp
nipkow@17629
  1245
nipkow@17629
  1246
lemma filter_eq_Cons_iff:
nipkow@17629
  1247
 "(filter P ys = x#xs) =
nipkow@17629
  1248
  (\<exists>us vs. ys = us @ x # vs \<and> (\<forall>u\<in>set us. \<not> P u) \<and> P x \<and> xs = filter P vs)"
nipkow@17629
  1249
by(auto dest:filter_eq_ConsD)
nipkow@17629
  1250
nipkow@17629
  1251
lemma Cons_eq_filter_iff:
nipkow@17629
  1252
 "(x#xs = filter P ys) =
nipkow@17629
  1253
  (\<exists>us vs. ys = us @ x # vs \<and> (\<forall>u\<in>set us. \<not> P u) \<and> P x \<and> xs = filter P vs)"
nipkow@17629
  1254
by(auto dest:Cons_eq_filterD)
nipkow@17629
  1255
krauss@44013
  1256
lemma filter_cong[fundef_cong]:
nipkow@17501
  1257
 "xs = ys \<Longrightarrow> (\<And>x. x \<in> set ys \<Longrightarrow> P x = Q x) \<Longrightarrow> filter P xs = filter Q ys"
nipkow@17501
  1258
apply simp
nipkow@17501
  1259
apply(erule thin_rl)
nipkow@17501
  1260
by (induct ys) simp_all
nipkow@17501
  1261
nipkow@15281
  1262
haftmann@26442
  1263
subsubsection {* List partitioning *}
haftmann@26442
  1264
haftmann@26442
  1265
primrec partition :: "('a \<Rightarrow> bool) \<Rightarrow>'a list \<Rightarrow> 'a list \<times> 'a list" where
haftmann@26442
  1266
  "partition P [] = ([], [])"
haftmann@26442
  1267
  | "partition P (x # xs) = 
haftmann@26442
  1268
      (let (yes, no) = partition P xs
haftmann@26442
  1269
      in if P x then (x # yes, no) else (yes, x # no))"
haftmann@26442
  1270
haftmann@26442
  1271
lemma partition_filter1:
haftmann@26442
  1272
    "fst (partition P xs) = filter P xs"
haftmann@26442
  1273
by (induct xs) (auto simp add: Let_def split_def)
haftmann@26442
  1274
haftmann@26442
  1275
lemma partition_filter2:
haftmann@26442
  1276
    "snd (partition P xs) = filter (Not o P) xs"
haftmann@26442
  1277
by (induct xs) (auto simp add: Let_def split_def)
haftmann@26442
  1278
haftmann@26442
  1279
lemma partition_P:
haftmann@26442
  1280
  assumes "partition P xs = (yes, no)"
haftmann@26442
  1281
  shows "(\<forall>p \<in> set yes.  P p) \<and> (\<forall>p  \<in> set no. \<not> P p)"
haftmann@26442
  1282
proof -
haftmann@26442
  1283
  from assms have "yes = fst (partition P xs)" and "no = snd (partition P xs)"
haftmann@26442
  1284
    by simp_all
haftmann@26442
  1285
  then show ?thesis by (simp_all add: partition_filter1 partition_filter2)
haftmann@26442
  1286
qed
haftmann@26442
  1287
haftmann@26442
  1288
lemma partition_set:
haftmann@26442
  1289
  assumes "partition P xs = (yes, no)"
haftmann@26442
  1290
  shows "set yes \<union> set no = set xs"
haftmann@26442
  1291
proof -
haftmann@26442
  1292
  from assms have "yes = fst (partition P xs)" and "no = snd (partition P xs)"
haftmann@26442
  1293
    by simp_all
haftmann@26442
  1294
  then show ?thesis by (auto simp add: partition_filter1 partition_filter2) 
haftmann@26442
  1295
qed
haftmann@26442
  1296
hoelzl@33639
  1297
lemma partition_filter_conv[simp]:
hoelzl@33639
  1298
  "partition f xs = (filter f xs,filter (Not o f) xs)"
hoelzl@33639
  1299
unfolding partition_filter2[symmetric]
hoelzl@33639
  1300
unfolding partition_filter1[symmetric] by simp
hoelzl@33639
  1301
hoelzl@33639
  1302
declare partition.simps[simp del]
haftmann@26442
  1303
wenzelm@35115
  1304
nipkow@15392
  1305
subsubsection {* @{text concat} *}
wenzelm@13114
  1306
wenzelm@13142
  1307
lemma concat_append [simp]: "concat (xs @ ys) = concat xs @ concat ys"
nipkow@13145
  1308
by (induct xs) auto
wenzelm@13114
  1309
paulson@18447
  1310
lemma concat_eq_Nil_conv [simp]: "(concat xss = []) = (\<forall>xs \<in> set xss. xs = [])"
nipkow@13145
  1311
by (induct xss) auto
wenzelm@13114
  1312
paulson@18447
  1313
lemma Nil_eq_concat_conv [simp]: "([] = concat xss) = (\<forall>xs \<in> set xss. xs = [])"
nipkow@13145
  1314
by (induct xss) auto
wenzelm@13114
  1315
nipkow@24308
  1316
lemma set_concat [simp]: "set (concat xs) = (UN x:set xs. set x)"
nipkow@13145
  1317
by (induct xs) auto
wenzelm@13114
  1318
nipkow@24476
  1319
lemma concat_map_singleton[simp]: "concat(map (%x. [f x]) xs) = map f xs"
nipkow@24349
  1320
by (induct xs) auto
nipkow@24349
  1321
wenzelm@13142
  1322
lemma map_concat: "map f (concat xs) = concat (map (map f) xs)"
nipkow@13145
  1323
by (induct xs) auto
wenzelm@13114
  1324
wenzelm@13142
  1325
lemma filter_concat: "filter p (concat xs) = concat (map (filter p) xs)"
nipkow@13145
  1326
by (induct xs) auto
wenzelm@13114
  1327
wenzelm@13142
  1328
lemma rev_concat: "rev (concat xs) = concat (map rev (rev xs))"
nipkow@13145
  1329
by (induct xs) auto
wenzelm@13114
  1330
bulwahn@40365
  1331
lemma concat_eq_concat_iff: "\<forall>(x, y) \<in> set (zip xs ys). length x = length y ==> length xs = length ys ==> (concat xs = concat ys) = (xs = ys)"
bulwahn@40365
  1332
proof (induct xs arbitrary: ys)
bulwahn@40365
  1333
  case (Cons x xs ys)
bulwahn@40365
  1334
  thus ?case by (cases ys) auto
bulwahn@40365
  1335
qed (auto)
bulwahn@40365
  1336
bulwahn@40365
  1337
lemma concat_injective: "concat xs = concat ys ==> length xs = length ys ==> \<forall>(x, y) \<in> set (zip xs ys). length x = length y ==> xs = ys"
bulwahn@40365
  1338
by (simp add: concat_eq_concat_iff)
bulwahn@40365
  1339
wenzelm@13114
  1340
nipkow@15392
  1341
subsubsection {* @{text nth} *}
wenzelm@13114
  1342
haftmann@29827
  1343
lemma nth_Cons_0 [simp, code]: "(x # xs)!0 = x"
nipkow@13145
  1344
by auto
wenzelm@13114
  1345
haftmann@29827
  1346
lemma nth_Cons_Suc [simp, code]: "(x # xs)!(Suc n) = xs!n"
nipkow@13145
  1347
by auto
wenzelm@13114
  1348
wenzelm@13142
  1349
declare nth.simps [simp del]
wenzelm@13114
  1350
nipkow@41842
  1351
lemma nth_Cons_pos[simp]: "0 < n \<Longrightarrow> (x#xs) ! n = xs ! (n - 1)"
nipkow@41842
  1352
by(auto simp: Nat.gr0_conv_Suc)
nipkow@41842
  1353
wenzelm@13114
  1354
lemma nth_append:
nipkow@24526
  1355
  "(xs @ ys)!n = (if n < length xs then xs!n else ys!(n - length xs))"
nipkow@24526
  1356
apply (induct xs arbitrary: n, simp)
paulson@14208
  1357
apply (case_tac n, auto)
nipkow@13145
  1358
done
wenzelm@13114
  1359
nipkow@14402
  1360
lemma nth_append_length [simp]: "(xs @ x # ys) ! length xs = x"
wenzelm@25221
  1361
by (induct xs) auto
nipkow@14402
  1362
nipkow@14402
  1363
lemma nth_append_length_plus[simp]: "(xs @ ys) ! (length xs + n) = ys ! n"
wenzelm@25221
  1364
by (induct xs) auto
nipkow@14402
  1365
nipkow@24526
  1366
lemma nth_map [simp]: "n < length xs ==> (map f xs)!n = f(xs!n)"
nipkow@24526
  1367
apply (induct xs arbitrary: n, simp)
paulson@14208
  1368
apply (case_tac n, auto)
nipkow@13145
  1369
done
wenzelm@13114
  1370
noschinl@45841
  1371
lemma nth_tl:
noschinl@45841
  1372
  assumes "n < length (tl x)" shows "tl x ! n = x ! Suc n"
noschinl@45841
  1373
using assms by (induct x) auto
noschinl@45841
  1374
nipkow@18423
  1375
lemma hd_conv_nth: "xs \<noteq> [] \<Longrightarrow> hd xs = xs!0"
nipkow@18423
  1376
by(cases xs) simp_all
nipkow@18423
  1377
nipkow@18049
  1378
nipkow@18049
  1379
lemma list_eq_iff_nth_eq:
nipkow@24526
  1380
 "(xs = ys) = (length xs = length ys \<and> (ALL i<length xs. xs!i = ys!i))"
nipkow@24526
  1381
apply(induct xs arbitrary: ys)
paulson@24632
  1382
 apply force
nipkow@18049
  1383
apply(case_tac ys)
nipkow@18049
  1384
 apply simp
nipkow@18049
  1385
apply(simp add:nth_Cons split:nat.split)apply blast
nipkow@18049
  1386
done
nipkow@18049
  1387
wenzelm@13142
  1388
lemma set_conv_nth: "set xs = {xs!i | i. i < length xs}"
paulson@15251
  1389
apply (induct xs, simp, simp)
nipkow@13145
  1390
apply safe
paulson@24632
  1391
apply (metis nat_case_0 nth.simps zero_less_Suc)
paulson@24632
  1392
apply (metis less_Suc_eq_0_disj nth_Cons_Suc)
paulson@14208
  1393
apply (case_tac i, simp)
paulson@24632
  1394
apply (metis diff_Suc_Suc nat_case_Suc nth.simps zero_less_diff)
nipkow@13145
  1395
done
wenzelm@13114
  1396
nipkow@17501
  1397
lemma in_set_conv_nth: "(x \<in> set xs) = (\<exists>i < length xs. xs!i = x)"
nipkow@17501
  1398
by(auto simp:set_conv_nth)
nipkow@17501
  1399
nipkow@13145
  1400
lemma list_ball_nth: "[| n < length xs; !x : set xs. P x|] ==> P(xs!n)"
nipkow@13145
  1401
by (auto simp add: set_conv_nth)
wenzelm@13114
  1402
wenzelm@13142
  1403
lemma nth_mem [simp]: "n < length xs ==> xs!n : set xs"
nipkow@13145
  1404
by (auto simp add: set_conv_nth)
wenzelm@13114
  1405
wenzelm@13114
  1406
lemma all_nth_imp_all_set:
nipkow@13145
  1407
"[| !i < length xs. P(xs!i); x : set xs|] ==> P x"
nipkow@13145
  1408
by (auto simp add: set_conv_nth)
wenzelm@13114
  1409
wenzelm@13114
  1410
lemma all_set_conv_all_nth:
nipkow@13145
  1411
"(\<forall>x \<in> set xs. P x) = (\<forall>i. i < length xs --> P (xs ! i))"
nipkow@13145
  1412
by (auto simp add: set_conv_nth)
wenzelm@13114
  1413
kleing@25296
  1414
lemma rev_nth:
kleing@25296
  1415
  "n < size xs \<Longrightarrow> rev xs ! n = xs ! (length xs - Suc n)"
kleing@25296
  1416
proof (induct xs arbitrary: n)
kleing@25296
  1417
  case Nil thus ?case by simp
kleing@25296
  1418
next
kleing@25296
  1419
  case (Cons x xs)
kleing@25296
  1420
  hence n: "n < Suc (length xs)" by simp
kleing@25296
  1421
  moreover
kleing@25296
  1422
  { assume "n < length xs"
kleing@25296
  1423
    with n obtain n' where "length xs - n = Suc n'"
kleing@25296
  1424
      by (cases "length xs - n", auto)
kleing@25296
  1425
    moreover
kleing@25296
  1426
    then have "length xs - Suc n = n'" by simp
kleing@25296
  1427
    ultimately
kleing@25296
  1428
    have "xs ! (length xs - Suc n) = (x # xs) ! (length xs - n)" by simp
kleing@25296
  1429
  }
kleing@25296
  1430
  ultimately
kleing@25296
  1431
  show ?case by (clarsimp simp add: Cons nth_append)
kleing@25296
  1432
qed
wenzelm@13114
  1433
nipkow@31159
  1434
lemma Skolem_list_nth:
nipkow@31159
  1435
  "(ALL i<k. EX x. P i x) = (EX xs. size xs = k & (ALL i<k. P i (xs!i)))"
nipkow@31159
  1436
  (is "_ = (EX xs. ?P k xs)")
nipkow@31159
  1437
proof(induct k)
nipkow@31159
  1438
  case 0 show ?case by simp
nipkow@31159
  1439
next
nipkow@31159
  1440
  case (Suc k)
nipkow@31159
  1441
  show ?case (is "?L = ?R" is "_ = (EX xs. ?P' xs)")
nipkow@31159
  1442
  proof
nipkow@31159
  1443
    assume "?R" thus "?L" using Suc by auto
nipkow@31159
  1444
  next
nipkow@31159
  1445
    assume "?L"
nipkow@31159
  1446
    with Suc obtain x xs where "?P k xs & P k x" by (metis less_Suc_eq)
nipkow@31159
  1447
    hence "?P'(xs@[x])" by(simp add:nth_append less_Suc_eq)
nipkow@31159
  1448
    thus "?R" ..
nipkow@31159
  1449
  qed
nipkow@31159
  1450
qed
nipkow@31159
  1451
nipkow@31159
  1452
nipkow@15392
  1453
subsubsection {* @{text list_update} *}
wenzelm@13114
  1454
nipkow@24526
  1455
lemma length_list_update [simp]: "length(xs[i:=x]) = length xs"
nipkow@24526
  1456
by (induct xs arbitrary: i) (auto split: nat.split)
wenzelm@13114
  1457
wenzelm@13114
  1458
lemma nth_list_update:
nipkow@24526
  1459
"i < length xs==> (xs[i:=x])!j = (if i = j then x else xs!j)"
nipkow@24526
  1460
by (induct xs arbitrary: i j) (auto simp add: nth_Cons split: nat.split)
wenzelm@13114
  1461
wenzelm@13142
  1462
lemma nth_list_update_eq [simp]: "i < length xs ==> (xs[i:=x])!i = x"
nipkow@13145
  1463
by (simp add: nth_list_update)
wenzelm@13114
  1464
nipkow@24526
  1465
lemma nth_list_update_neq [simp]: "i \<noteq> j ==> xs[i:=x]!j = xs!j"
nipkow@24526
  1466
by (induct xs arbitrary: i j) (auto simp add: nth_Cons split: nat.split)
wenzelm@13114
  1467
nipkow@24526
  1468
lemma list_update_id[simp]: "xs[i := xs!i] = xs"
nipkow@24526
  1469
by (induct xs arbitrary: i) (simp_all split:nat.splits)
nipkow@24526
  1470
nipkow@24526
  1471
lemma list_update_beyond[simp]: "length xs \<le> i \<Longrightarrow> xs[i:=x] = xs"
nipkow@24526
  1472
apply (induct xs arbitrary: i)
nipkow@17501
  1473
 apply simp
nipkow@17501
  1474
apply (case_tac i)
nipkow@17501
  1475
apply simp_all
nipkow@17501
  1476
done
nipkow@17501
  1477
nipkow@31077
  1478
lemma list_update_nonempty[simp]: "xs[k:=x] = [] \<longleftrightarrow> xs=[]"
nipkow@31077
  1479
by(metis length_0_conv length_list_update)
nipkow@31077
  1480
wenzelm@13114
  1481
lemma list_update_same_conv:
nipkow@24526
  1482
"i < length xs ==> (xs[i := x] = xs) = (xs!i = x)"
nipkow@24526
  1483
by (induct xs arbitrary: i) (auto split: nat.split)
wenzelm@13114
  1484
nipkow@14187
  1485
lemma list_update_append1:
nipkow@24526
  1486
 "i < size xs \<Longrightarrow> (xs @ ys)[i:=x] = xs[i:=x] @ ys"
nipkow@24526
  1487
apply (induct xs arbitrary: i, simp)
nipkow@14187
  1488
apply(simp split:nat.split)
nipkow@14187
  1489
done
nipkow@14187
  1490
kleing@15868
  1491
lemma list_update_append:
nipkow@24526
  1492
  "(xs @ ys) [n:= x] = 
kleing@15868
  1493
  (if n < length xs then xs[n:= x] @ ys else xs @ (ys [n-length xs:= x]))"
nipkow@24526
  1494
by (induct xs arbitrary: n) (auto split:nat.splits)
kleing@15868
  1495
nipkow@14402
  1496
lemma list_update_length [simp]:
nipkow@14402
  1497
 "(xs @ x # ys)[length xs := y] = (xs @ y # ys)"
nipkow@14402
  1498
by (induct xs, auto)
nipkow@14402
  1499
nipkow@31264
  1500
lemma map_update: "map f (xs[k:= y]) = (map f xs)[k := f y]"
nipkow@31264
  1501
by(induct xs arbitrary: k)(auto split:nat.splits)
nipkow@31264
  1502
nipkow@31264
  1503
lemma rev_update:
nipkow@31264
  1504
  "k < length xs \<Longrightarrow> rev (xs[k:= y]) = (rev xs)[length xs - k - 1 := y]"
nipkow@31264
  1505
by (induct xs arbitrary: k) (auto simp: list_update_append split:nat.splits)
nipkow@31264
  1506
wenzelm@13114
  1507
lemma update_zip:
nipkow@31080
  1508
  "(zip xs ys)[i:=xy] = zip (xs[i:=fst xy]) (ys[i:=snd xy])"
nipkow@24526
  1509
by (induct ys arbitrary: i xy xs) (auto, case_tac xs, auto split: nat.split)
nipkow@24526
  1510
nipkow@24526
  1511
lemma set_update_subset_insert: "set(xs[i:=x]) <= insert x (set xs)"
nipkow@24526
  1512
by (induct xs arbitrary: i) (auto split: nat.split)
wenzelm@13114
  1513
wenzelm@13114
  1514
lemma set_update_subsetI: "[| set xs <= A; x:A |] ==> set(xs[i := x]) <= A"
nipkow@13145
  1515
by (blast dest!: set_update_subset_insert [THEN subsetD])
wenzelm@13114
  1516
nipkow@24526
  1517
lemma set_update_memI: "n < length xs \<Longrightarrow> x \<in> set (xs[n := x])"
nipkow@24526
  1518
by (induct xs arbitrary: n) (auto split:nat.splits)
kleing@15868
  1519
nipkow@31077
  1520
lemma list_update_overwrite[simp]:
haftmann@24796
  1521
  "xs [i := x, i := y] = xs [i := y]"
nipkow@31077
  1522
apply (induct xs arbitrary: i) apply simp
nipkow@31077
  1523
apply (case_tac i, simp_all)
haftmann@24796
  1524
done
haftmann@24796
  1525
haftmann@24796
  1526
lemma list_update_swap:
haftmann@24796
  1527
  "i \<noteq> i' \<Longrightarrow> xs [i := x, i' := x'] = xs [i' := x', i := x]"
haftmann@24796
  1528
apply (induct xs arbitrary: i i')
haftmann@24796
  1529
apply simp
haftmann@24796
  1530
apply (case_tac i, case_tac i')
haftmann@24796
  1531
apply auto
haftmann@24796
  1532
apply (case_tac i')
haftmann@24796
  1533
apply auto
haftmann@24796
  1534
done
haftmann@24796
  1535
haftmann@29827
  1536
lemma list_update_code [code]:
haftmann@29827
  1537
  "[][i := y] = []"
haftmann@29827
  1538
  "(x # xs)[0 := y] = y # xs"
haftmann@29827
  1539
  "(x # xs)[Suc i := y] = x # xs[i := y]"
haftmann@29827
  1540
  by simp_all
haftmann@29827
  1541
wenzelm@13114
  1542
nipkow@15392
  1543
subsubsection {* @{text last} and @{text butlast} *}
wenzelm@13114
  1544
wenzelm@13142
  1545
lemma last_snoc [simp]: "last (xs @ [x]) = x"
nipkow@13145
  1546
by (induct xs) auto
wenzelm@13114
  1547
wenzelm@13142
  1548
lemma butlast_snoc [simp]: "butlast (xs @ [x]) = xs"
nipkow@13145
  1549
by (induct xs) auto
wenzelm@13114
  1550
nipkow@14302
  1551
lemma last_ConsL: "xs = [] \<Longrightarrow> last(x#xs) = x"
huffman@44921
  1552
  by simp
nipkow@14302
  1553
nipkow@14302
  1554
lemma last_ConsR: "xs \<noteq> [] \<Longrightarrow> last(x#xs) = last xs"
huffman@44921
  1555
  by simp
nipkow@14302
  1556
nipkow@14302
  1557
lemma last_append: "last(xs @ ys) = (if ys = [] then last xs else last ys)"
nipkow@14302
  1558
by (induct xs) (auto)
nipkow@14302
  1559
nipkow@14302
  1560
lemma last_appendL[simp]: "ys = [] \<Longrightarrow> last(xs @ ys) = last xs"
nipkow@14302
  1561
by(simp add:last_append)
nipkow@14302
  1562
nipkow@14302
  1563
lemma last_appendR[simp]: "ys \<noteq> [] \<Longrightarrow> last(xs @ ys) = last ys"
nipkow@14302
  1564
by(simp add:last_append)
nipkow@14302
  1565
noschinl@45841
  1566
lemma last_tl: "xs = [] \<or> tl xs \<noteq> [] \<Longrightarrow>last (tl xs) = last xs"
noschinl@45841
  1567
by (induct xs) simp_all
noschinl@45841
  1568
noschinl@45841
  1569
lemma butlast_tl: "butlast (tl xs) = tl (butlast xs)"
noschinl@45841
  1570
by (induct xs) simp_all
noschinl@45841
  1571
nipkow@17762
  1572
lemma hd_rev: "xs \<noteq> [] \<Longrightarrow> hd(rev xs) = last xs"
nipkow@17762
  1573
by(rule rev_exhaust[of xs]) simp_all
nipkow@17762
  1574
nipkow@17762
  1575
lemma last_rev: "xs \<noteq> [] \<Longrightarrow> last(rev xs) = hd xs"
nipkow@17762
  1576
by(cases xs) simp_all
nipkow@17762
  1577
nipkow@17765
  1578
lemma last_in_set[simp]: "as \<noteq> [] \<Longrightarrow> last as \<in> set as"
nipkow@17765
  1579
by (induct as) auto
nipkow@17762
  1580
wenzelm@13142
  1581
lemma length_butlast [simp]: "length (butlast xs) = length xs - 1"
nipkow@13145
  1582
by (induct xs rule: rev_induct) auto
wenzelm@13114
  1583
wenzelm@13114
  1584
lemma butlast_append:
nipkow@24526
  1585
  "butlast (xs @ ys) = (if ys = [] then butlast xs else xs @ butlast ys)"
nipkow@24526
  1586
by (induct xs arbitrary: ys) auto
wenzelm@13114
  1587
wenzelm@13142
  1588
lemma append_butlast_last_id [simp]:
nipkow@13145
  1589
"xs \<noteq> [] ==> butlast xs @ [last xs] = xs"
nipkow@13145
  1590
by (induct xs) auto
wenzelm@13114
  1591
wenzelm@13142
  1592
lemma in_set_butlastD: "x : set (butlast xs) ==> x : set xs"
nipkow@13145
  1593
by (induct xs) (auto split: split_if_asm)
wenzelm@13114
  1594
wenzelm@13114
  1595
lemma in_set_butlast_appendI:
nipkow@13145
  1596
"x : set (butlast xs) | x : set (butlast ys) ==> x : set (butlast (xs @ ys))"
nipkow@13145
  1597
by (auto dest: in_set_butlastD simp add: butlast_append)
wenzelm@13114
  1598
nipkow@24526
  1599
lemma last_drop[simp]: "n < length xs \<Longrightarrow> last (drop n xs) = last xs"
nipkow@24526
  1600
apply (induct xs arbitrary: n)
nipkow@17501
  1601
 apply simp
nipkow@17501
  1602
apply (auto split:nat.split)
nipkow@17501
  1603
done
nipkow@17501
  1604
noschinl@45841
  1605
lemma nth_butlast:
noschinl@45841
  1606
  assumes "n < length (butlast xs)" shows "butlast xs ! n = xs ! n"
noschinl@45841
  1607
proof (cases xs)
noschinl@45841
  1608
  case (Cons y ys)
noschinl@45841
  1609
  moreover from assms have "butlast xs ! n = (butlast xs @ [last xs]) ! n"
noschinl@45841
  1610
    by (simp add: nth_append)
noschinl@45841
  1611
  ultimately show ?thesis using append_butlast_last_id by simp
noschinl@45841
  1612
qed simp
noschinl@45841
  1613
huffman@30128
  1614
lemma last_conv_nth: "xs\<noteq>[] \<Longrightarrow> last xs = xs!(length xs - 1)"
nipkow@17589
  1615
by(induct xs)(auto simp:neq_Nil_conv)
nipkow@17589
  1616
huffman@30128
  1617
lemma butlast_conv_take: "butlast xs = take (length xs - 1) xs"
huffman@26584
  1618
by (induct xs, simp, case_tac xs, simp_all)
huffman@26584
  1619
nipkow@31077
  1620
lemma last_list_update:
nipkow@31077
  1621
  "xs \<noteq> [] \<Longrightarrow> last(xs[k:=x]) = (if k = size xs - 1 then x else last xs)"
nipkow@31077
  1622
by (auto simp: last_conv_nth)
nipkow@31077
  1623
nipkow@31077
  1624
lemma butlast_list_update:
nipkow@31077
  1625
  "butlast(xs[k:=x]) =
nipkow@31077
  1626
 (if k = size xs - 1 then butlast xs else (butlast xs)[k:=x])"
nipkow@31077
  1627
apply(cases xs rule:rev_cases)
nipkow@31077
  1628
apply simp
nipkow@31077
  1629
apply(simp add:list_update_append split:nat.splits)
nipkow@31077
  1630
done
nipkow@31077
  1631
haftmann@36851
  1632
lemma last_map:
haftmann@36851
  1633
  "xs \<noteq> [] \<Longrightarrow> last (map f xs) = f (last xs)"
haftmann@36851
  1634
  by (cases xs rule: rev_cases) simp_all
haftmann@36851
  1635
haftmann@36851
  1636
lemma map_butlast:
haftmann@36851
  1637
  "map f (butlast xs) = butlast (map f xs)"
haftmann@36851
  1638
  by (induct xs) simp_all
haftmann@36851
  1639
nipkow@40230
  1640
lemma snoc_eq_iff_butlast:
nipkow@40230
  1641
  "xs @ [x] = ys \<longleftrightarrow> (ys \<noteq> [] & butlast ys = xs & last ys = x)"
nipkow@40230
  1642
by (metis append_butlast_last_id append_is_Nil_conv butlast_snoc last_snoc not_Cons_self)
nipkow@40230
  1643
haftmann@24796
  1644
nipkow@15392
  1645
subsubsection {* @{text take} and @{text drop} *}
wenzelm@13114
  1646
wenzelm@13142
  1647
lemma take_0 [simp]: "take 0 xs = []"
nipkow@13145
  1648
by (induct xs) auto
wenzelm@13114
  1649
wenzelm@13142
  1650
lemma drop_0 [simp]: "drop 0 xs = xs"
nipkow@13145
  1651
by (induct xs) auto
wenzelm@13114
  1652
wenzelm@13142
  1653
lemma take_Suc_Cons [simp]: "take (Suc n) (x # xs) = x # take n xs"
nipkow@13145
  1654
by simp
wenzelm@13114
  1655
wenzelm@13142
  1656
lemma drop_Suc_Cons [simp]: "drop (Suc n) (x # xs) = drop n xs"
nipkow@13145
  1657
by simp
wenzelm@13114
  1658
wenzelm@13142
  1659
declare take_Cons [simp del] and drop_Cons [simp del]
wenzelm@13114
  1660
huffman@30128
  1661
lemma take_1_Cons [simp]: "take 1 (x # xs) = [x]"
huffman@30128
  1662
  unfolding One_nat_def by simp
huffman@30128
  1663
huffman@30128
  1664
lemma drop_1_Cons [simp]: "drop 1 (x # xs) = xs"
huffman@30128
  1665
  unfolding One_nat_def by simp
huffman@30128
  1666
nipkow@15110
  1667
lemma take_Suc: "xs ~= [] ==> take (Suc n) xs = hd xs # take n (tl xs)"
nipkow@15110
  1668
by(clarsimp simp add:neq_Nil_conv)
nipkow@15110
  1669
nipkow@14187
  1670
lemma drop_Suc: "drop (Suc n) xs = drop n (tl xs)"
nipkow@14187
  1671
by(cases xs, simp_all)
nipkow@14187
  1672
huffman@26584
  1673
lemma take_tl: "take n (tl xs) = tl (take (Suc n) xs)"
huffman@26584
  1674
by (induct xs arbitrary: n) simp_all
huffman@26584
  1675
nipkow@24526
  1676
lemma drop_tl: "drop n (tl xs) = tl(drop n xs)"
nipkow@24526
  1677
by(induct xs arbitrary: n, simp_all add:drop_Cons drop_Suc split:nat.split)
nipkow@24526
  1678
huffman@26584
  1679
lemma tl_take: "tl (take n xs) = take (n - 1) (tl xs)"
huffman@26584
  1680
by (cases n, simp, cases xs, auto)
huffman@26584
  1681
huffman@26584
  1682
lemma tl_drop: "tl (drop n xs) = drop n (tl xs)"
huffman@26584
  1683
by (simp only: drop_tl)
huffman@26584
  1684
nipkow@24526
  1685
lemma nth_via_drop: "drop n xs = y#ys \<Longrightarrow> xs!n = y"
nipkow@24526
  1686
apply (induct xs arbitrary: n, simp)
nipkow@14187
  1687
apply(simp add:drop_Cons nth_Cons split:nat.splits)
nipkow@14187
  1688
done
nipkow@14187
  1689
nipkow@13913
  1690
lemma take_Suc_conv_app_nth:
nipkow@24526
  1691
  "i < length xs \<Longrightarrow> take (Suc i) xs = take i xs @ [xs!i]"
nipkow@24526
  1692
apply (induct xs arbitrary: i, simp)
paulson@14208
  1693
apply (case_tac i, auto)
nipkow@13913
  1694
done
nipkow@13913
  1695
mehta@14591
  1696
lemma drop_Suc_conv_tl:
nipkow@24526
  1697
  "i < length xs \<Longrightarrow> (xs!i) # (drop (Suc i) xs) = drop i xs"
nipkow@24526
  1698
apply (induct xs arbitrary: i, simp)
mehta@14591
  1699
apply (case_tac i, auto)
mehta@14591
  1700
done
mehta@14591
  1701
nipkow@24526
  1702
lemma length_take [simp]: "length (take n xs) = min (length xs) n"
nipkow@24526
  1703
by (induct n arbitrary: xs) (auto, case_tac xs, auto)
nipkow@24526
  1704
nipkow@24526
  1705
lemma length_drop [simp]: "length (drop n xs) = (length xs - n)"
nipkow@24526
  1706
by (induct n arbitrary: xs) (auto, case_tac xs, auto)
nipkow@24526
  1707
nipkow@24526
  1708
lemma take_all [simp]: "length xs <= n ==> take n xs = xs"
nipkow@24526
  1709
by (induct n arbitrary: xs) (auto, case_tac xs, auto)
nipkow@24526
  1710
nipkow@24526
  1711
lemma drop_all [simp]: "length xs <= n ==> drop n xs = []"
nipkow@24526
  1712
by (induct n arbitrary: xs) (auto, case_tac xs, auto)
wenzelm@13114
  1713
wenzelm@13142
  1714
lemma take_append [simp]:
nipkow@24526
  1715
  "take n (xs @ ys) = (take n xs @ take (n - length xs) ys)"
nipkow@24526
  1716
by (induct n arbitrary: xs) (auto, case_tac xs, auto)
wenzelm@13114
  1717
wenzelm@13142
  1718
lemma drop_append [simp]:
nipkow@24526
  1719
  "drop n (xs @ ys) = drop n xs @ drop (n - length xs) ys"
nipkow@24526
  1720
by (induct n arbitrary: xs) (auto, case_tac xs, auto)
nipkow@24526
  1721
nipkow@24526
  1722
lemma take_take [simp]: "take n (take m xs) = take (min n m) xs"
nipkow@24526
  1723
apply (induct m arbitrary: xs n, auto)
paulson@14208
  1724
apply (case_tac xs, auto)
nipkow@15236
  1725
apply (case_tac n, auto)
nipkow@13145
  1726
done
wenzelm@13114
  1727
nipkow@24526
  1728
lemma drop_drop [simp]: "drop n (drop m xs) = drop (n + m) xs"
nipkow@24526
  1729
apply (induct m arbitrary: xs, auto)
paulson@14208
  1730
apply (case_tac xs, auto)
nipkow@13145
  1731
done
wenzelm@13114
  1732
nipkow@24526
  1733
lemma take_drop: "take n (drop m xs) = drop m (take (n + m) xs)"
nipkow@24526
  1734
apply (induct m arbitrary: xs n, auto)
paulson@14208
  1735
apply (case_tac xs, auto)
nipkow@13145
  1736
done
wenzelm@13114
  1737
nipkow@24526
  1738
lemma drop_take: "drop n (take m xs) = take (m-n) (drop n xs)"
nipkow@24526
  1739
apply(induct xs arbitrary: m n)
nipkow@14802
  1740
 apply simp
nipkow@14802
  1741
apply(simp add: take_Cons drop_Cons split:nat.split)
nipkow@14802
  1742
done
nipkow@14802
  1743
nipkow@24526
  1744
lemma append_take_drop_id [simp]: "take n xs @ drop n xs = xs"
nipkow@24526
  1745
apply (induct n arbitrary: xs, auto)
paulson@14208
  1746
apply (case_tac xs, auto)
nipkow@13145
  1747
done
wenzelm@13114
  1748
nipkow@24526
  1749
lemma take_eq_Nil[simp]: "(take n xs = []) = (n = 0 \<or> xs = [])"
nipkow@24526
  1750
apply(induct xs arbitrary: n)
nipkow@15110
  1751
 apply simp
nipkow@15110
  1752
apply(simp add:take_Cons split:nat.split)
nipkow@15110
  1753
done
nipkow@15110
  1754
nipkow@24526
  1755
lemma drop_eq_Nil[simp]: "(drop n xs = []) = (length xs <= n)"
nipkow@24526
  1756
apply(induct xs arbitrary: n)
nipkow@15110
  1757
apply simp
nipkow@15110
  1758
apply(simp add:drop_Cons split:nat.split)
nipkow@15110
  1759
done
nipkow@15110
  1760
nipkow@24526
  1761
lemma take_map: "take n (map f xs) = map f (take n xs)"
nipkow@24526
  1762
apply (induct n arbitrary: xs, auto)
paulson@14208
  1763
apply (case_tac xs, auto)
nipkow@13145
  1764
done
wenzelm@13114
  1765
nipkow@24526
  1766
lemma drop_map: "drop n (map f xs) = map f (drop n xs)"
nipkow@24526
  1767
apply (induct n arbitrary: xs, auto)
paulson@14208
  1768
apply (case_tac xs, auto)
nipkow@13145
  1769
done
wenzelm@13114
  1770
nipkow@24526
  1771
lemma rev_take: "rev (take i xs) = drop (length xs - i) (rev xs)"
nipkow@24526
  1772
apply (induct xs arbitrary: i, auto)
paulson@14208
  1773
apply (case_tac i, auto)
nipkow@13145
  1774
done
wenzelm@13114
  1775
nipkow@24526
  1776
lemma rev_drop: "rev (drop i xs) = take (length xs - i) (rev xs)"
nipkow@24526
  1777
apply (induct xs arbitrary: i, auto)
paulson@14208
  1778
apply (case_tac i, auto)
nipkow@13145
  1779
done
wenzelm@13114
  1780
nipkow@24526
  1781
lemma nth_take [simp]: "i < n ==> (take n xs)!i = xs!i"
nipkow@24526
  1782
apply (induct xs arbitrary: i n, auto)
paulson@14208
  1783
apply (case_tac n, blast)
paulson@14208
  1784
apply (case_tac i, auto)
nipkow@13145
  1785
done
wenzelm@13114
  1786
wenzelm@13142
  1787
lemma nth_drop [simp]:
nipkow@24526
  1788
  "n + i <= length xs ==> (drop n xs)!i = xs!(n + i)"
nipkow@24526
  1789
apply (induct n arbitrary: xs i, auto)
paulson@14208
  1790
apply (case_tac xs, auto)
nipkow@13145
  1791
done
nipkow@3507
  1792
huffman@26584
  1793
lemma butlast_take:
huffman@30128
  1794
  "n <= length xs ==> butlast (take n xs) = take (n - 1) xs"
huffman@26584
  1795
by (simp add: butlast_conv_take min_max.inf_absorb1 min_max.inf_absorb2)
huffman@26584
  1796
huffman@26584
  1797
lemma butlast_drop: "butlast (drop n xs) = drop n (butlast xs)"
huffman@30128
  1798
by (simp add: butlast_conv_take drop_take add_ac)
huffman@26584
  1799
huffman@26584
  1800
lemma take_butlast: "n < length xs ==> take n (butlast xs) = take n xs"
huffman@26584
  1801
by (simp add: butlast_conv_take min_max.inf_absorb1)
huffman@26584
  1802
huffman@26584
  1803
lemma drop_butlast: "drop n (butlast xs) = butlast (drop n xs)"
huffman@30128
  1804
by (simp add: butlast_conv_take drop_take add_ac)
huffman@26584
  1805
bulwahn@46500
  1806
lemma hd_drop_conv_nth: "n < length xs \<Longrightarrow> hd(drop n xs) = xs!n"
nipkow@18423
  1807
by(simp add: hd_conv_nth)
nipkow@18423
  1808
nipkow@35248
  1809
lemma set_take_subset_set_take:
nipkow@35248
  1810
  "m <= n \<Longrightarrow> set(take m xs) <= set(take n xs)"
bulwahn@41463
  1811
apply (induct xs arbitrary: m n)
bulwahn@41463
  1812
apply simp
bulwahn@41463
  1813
apply (case_tac n)
bulwahn@41463
  1814
apply (auto simp: take_Cons)
bulwahn@41463
  1815
done
nipkow@35248
  1816
nipkow@24526
  1817
lemma set_take_subset: "set(take n xs) \<subseteq> set xs"
nipkow@24526
  1818
by(induct xs arbitrary: n)(auto simp:take_Cons split:nat.split)
nipkow@24526
  1819
nipkow@24526
  1820
lemma set_drop_subset: "set(drop n xs) \<subseteq> set xs"
nipkow@24526
  1821
by(induct xs arbitrary: n)(auto simp:drop_Cons split:nat.split)
nipkow@14025
  1822
nipkow@35248
  1823
lemma set_drop_subset_set_drop:
nipkow@35248
  1824
  "m >= n \<Longrightarrow> set(drop m xs) <= set(drop n xs)"
nipkow@35248
  1825
apply(induct xs arbitrary: m n)
nipkow@35248
  1826
apply(auto simp:drop_Cons split:nat.split)
nipkow@35248
  1827
apply (metis set_drop_subset subset_iff)
nipkow@35248
  1828
done
nipkow@35248
  1829
nipkow@14187
  1830
lemma in_set_takeD: "x : set(take n xs) \<Longrightarrow> x : set xs"
nipkow@14187
  1831
using set_take_subset by fast
nipkow@14187
  1832
nipkow@14187
  1833
lemma in_set_dropD: "x : set(drop n xs) \<Longrightarrow> x : set xs"
nipkow@14187
  1834
using set_drop_subset by fast
nipkow@14187
  1835
wenzelm@13114
  1836
lemma append_eq_conv_conj:
nipkow@24526
  1837
  "(xs @ ys = zs) = (xs = take (length xs) zs \<and> ys = drop (length xs) zs)"
nipkow@24526
  1838
apply (induct xs arbitrary: zs, simp, clarsimp)
paulson@14208
  1839
apply (case_tac zs, auto)
nipkow@13145
  1840
done
wenzelm@13142
  1841
nipkow@24526
  1842
lemma take_add: 
noschinl@42713
  1843
  "take (i+j) xs = take i xs @ take j (drop i xs)"
nipkow@24526
  1844
apply (induct xs arbitrary: i, auto) 
nipkow@24526
  1845
apply (case_tac i, simp_all)
paulson@14050
  1846
done
paulson@14050
  1847
nipkow@14300
  1848
lemma append_eq_append_conv_if:
nipkow@24526
  1849
 "(xs\<^isub>1 @ xs\<^isub>2 = ys\<^isub>1 @ ys\<^isub>2) =
nipkow@14300
  1850
  (if size xs\<^isub>1 \<le> size ys\<^isub>1
nipkow@14300
  1851
   then xs\<^isub>1 = take (size xs\<^isub>1) ys\<^isub>1 \<and> xs\<^isub>2 = drop (size xs\<^isub>1) ys\<^isub>1 @ ys\<^isub>2
nipkow@14300
  1852
   else take (size ys\<^isub>1) xs\<^isub>1 = ys\<^isub>1 \<and> drop (size ys\<^isub>1) xs\<^isub>1 @ xs\<^isub>2 = ys\<^isub>2)"
nipkow@24526
  1853
apply(induct xs\<^isub>1 arbitrary: ys\<^isub>1)
nipkow@14300
  1854
 apply simp
nipkow@14300
  1855
apply(case_tac ys\<^isub>1)
nipkow@14300
  1856
apply simp_all
nipkow@14300
  1857
done
nipkow@14300
  1858
nipkow@15110
  1859
lemma take_hd_drop:
huffman@30079
  1860
  "n < length xs \<Longrightarrow> take n xs @ [hd (drop n xs)] = take (Suc n) xs"
nipkow@24526
  1861
apply(induct xs arbitrary: n)
nipkow@15110
  1862
apply simp
nipkow@15110
  1863
apply(simp add:drop_Cons split:nat.split)
nipkow@15110
  1864
done
nipkow@15110
  1865
nipkow@17501
  1866
lemma id_take_nth_drop:
nipkow@17501
  1867
 "i < length xs \<Longrightarrow> xs = take i xs @ xs!i # drop (Suc i) xs" 
nipkow@17501
  1868
proof -
nipkow@17501
  1869
  assume si: "i < length xs"
nipkow@17501
  1870
  hence "xs = take (Suc i) xs @ drop (Suc i) xs" by auto
nipkow@17501
  1871
  moreover
nipkow@17501
  1872
  from si have "take (Suc i) xs = take i xs @ [xs!i]"
nipkow@17501
  1873
    apply (rule_tac take_Suc_conv_app_nth) by arith
nipkow@17501
  1874
  ultimately show ?thesis by auto
nipkow@17501
  1875
qed
nipkow@17501
  1876
  
nipkow@17501
  1877
lemma upd_conv_take_nth_drop:
nipkow@17501
  1878
 "i < length xs \<Longrightarrow> xs[i:=a] = take i xs @ a # drop (Suc i) xs"
nipkow@17501
  1879
proof -
nipkow@17501
  1880
  assume i: "i < length xs"
nipkow@17501
  1881
  have "xs[i:=a] = (take i xs @ xs!i # drop (Suc i) xs)[i:=a]"
nipkow@17501
  1882
    by(rule arg_cong[OF id_take_nth_drop[OF i]])
nipkow@17501
  1883
  also have "\<dots> = take i xs @ a # drop (Suc i) xs"
nipkow@17501
  1884
    using i by (simp add: list_update_append)
nipkow@17501
  1885
  finally show ?thesis .
nipkow@17501
  1886
qed
nipkow@17501
  1887
haftmann@24796
  1888
lemma nth_drop':
haftmann@24796
  1889
  "i < length xs \<Longrightarrow> xs ! i # drop (Suc i) xs = drop i xs"
haftmann@24796
  1890
apply (induct i arbitrary: xs)
haftmann@24796
  1891
apply (simp add: neq_Nil_conv)
haftmann@24796
  1892
apply (erule exE)+
haftmann@24796
  1893
apply simp
haftmann@24796
  1894
apply (case_tac xs)
haftmann@24796
  1895
apply simp_all
haftmann@24796
  1896
done
haftmann@24796
  1897
wenzelm@13114
  1898
nipkow@15392
  1899
subsubsection {* @{text takeWhile} and @{text dropWhile} *}
wenzelm@13114
  1900
hoelzl@33639
  1901
lemma length_takeWhile_le: "length (takeWhile P xs) \<le> length xs"
hoelzl@33639
  1902
  by (induct xs) auto
hoelzl@33639
  1903
wenzelm@13142
  1904
lemma takeWhile_dropWhile_id [simp]: "takeWhile P xs @ dropWhile P xs = xs"
nipkow@13145
  1905
by (induct xs) auto
wenzelm@13114
  1906
wenzelm@13142
  1907
lemma takeWhile_append1 [simp]:
nipkow@13145
  1908
"[| x:set xs; ~P(x)|] ==> takeWhile P (xs @ ys) = takeWhile P xs"
nipkow@13145
  1909
by (induct xs) auto
wenzelm@13114
  1910
wenzelm@13142
  1911
lemma takeWhile_append2 [simp]:
nipkow@13145
  1912
"(!!x. x : set xs ==> P x) ==> takeWhile P (xs @ ys) = xs @ takeWhile P ys"
nipkow@13145
  1913
by (induct xs) auto
wenzelm@13114
  1914
wenzelm@13142
  1915
lemma takeWhile_tail: "\<not> P x ==> takeWhile P (xs @ (x#l)) = takeWhile P xs"
nipkow@13145
  1916
by (induct xs) auto
wenzelm@13114
  1917
hoelzl@33639
  1918
lemma takeWhile_nth: "j < length (takeWhile P xs) \<Longrightarrow> takeWhile P xs ! j = xs ! j"
hoelzl@33639
  1919
apply (subst (3) takeWhile_dropWhile_id[symmetric]) unfolding nth_append by auto
hoelzl@33639
  1920
hoelzl@33639
  1921
lemma dropWhile_nth: "j < length (dropWhile P xs) \<Longrightarrow> dropWhile P xs ! j = xs ! (j + length (takeWhile P xs))"
hoelzl@33639
  1922
apply (subst (3) takeWhile_dropWhile_id[symmetric]) unfolding nth_append by auto
hoelzl@33639
  1923
hoelzl@33639
  1924
lemma length_dropWhile_le: "length (dropWhile P xs) \<le> length xs"
hoelzl@33639
  1925
by (induct xs) auto
hoelzl@33639
  1926
wenzelm@13142
  1927
lemma dropWhile_append1 [simp]:
nipkow@13145
  1928
"[| x : set xs; ~P(x)|] ==> dropWhile P (xs @ ys) = (dropWhile P xs)@ys"
nipkow@13145
  1929
by (induct xs) auto
wenzelm@13114
  1930
wenzelm@13142
  1931
lemma dropWhile_append2 [simp]:
nipkow@13145
  1932
"(!!x. x:set xs ==> P(x)) ==> dropWhile P (xs @ ys) = dropWhile P ys"
nipkow@13145
  1933
by (induct xs) auto
wenzelm@13114
  1934
noschinl@45841
  1935
lemma dropWhile_append3:
noschinl@45841
  1936
  "\<not> P y \<Longrightarrow>dropWhile P (xs @ y # ys) = dropWhile P xs @ y # ys"
noschinl@45841
  1937
by (induct xs) auto
noschinl@45841
  1938
noschinl@45841
  1939
lemma dropWhile_last:
noschinl@45841
  1940
  "x \<in> set xs \<Longrightarrow> \<not> P x \<Longrightarrow> last (dropWhile P xs) = last xs"
noschinl@45841
  1941
by (auto simp add: dropWhile_append3 in_set_conv_decomp)
noschinl@45841
  1942
noschinl@45841
  1943
lemma set_dropWhileD: "x \<in> set (dropWhile P xs) \<Longrightarrow> x \<in> set xs"
noschinl@45841
  1944
by (induct xs) (auto split: split_if_asm)
noschinl@45841
  1945
krauss@23971
  1946
lemma set_takeWhileD: "x : set (takeWhile P xs) ==> x : set xs \<and> P x"
nipkow@13145
  1947
by (induct xs) (auto split: split_if_asm)
wenzelm@13114
  1948
nipkow@13913
  1949
lemma takeWhile_eq_all_conv[simp]:
nipkow@13913
  1950
 "(takeWhile P xs = xs) = (\<forall>x \<in> set xs. P x)"
nipkow@13913
  1951
by(induct xs, auto)
nipkow@13913
  1952
nipkow@13913
  1953
lemma dropWhile_eq_Nil_conv[simp]:
nipkow@13913
  1954
 "(dropWhile P xs = []) = (\<forall>x \<in> set xs. P x)"
nipkow@13913
  1955
by(induct xs, auto)
nipkow@13913
  1956
nipkow@13913
  1957
lemma dropWhile_eq_Cons_conv:
nipkow@13913
  1958
 "(dropWhile P xs = y#ys) = (xs = takeWhile P xs @ y # ys & \<not> P y)"
nipkow@13913
  1959
by(induct xs, auto)
nipkow@13913
  1960
nipkow@31077
  1961
lemma distinct_takeWhile[simp]: "distinct xs ==> distinct (takeWhile P xs)"
nipkow@31077
  1962
by (induct xs) (auto dest: set_takeWhileD)
nipkow@31077
  1963
nipkow@31077
  1964
lemma distinct_dropWhile[simp]: "distinct xs ==> distinct (dropWhile P xs)"
nipkow@31077
  1965
by (induct xs) auto
nipkow@31077
  1966
hoelzl@33639
  1967
lemma takeWhile_map: "takeWhile P (map f xs) = map f (takeWhile (P \<circ> f) xs)"
hoelzl@33639
  1968
by (induct xs) auto
hoelzl@33639
  1969
hoelzl@33639
  1970
lemma dropWhile_map: "dropWhile P (map f xs) = map f (dropWhile (P \<circ> f) xs)"
hoelzl@33639
  1971
by (induct xs) auto
hoelzl@33639
  1972
hoelzl@33639
  1973
lemma takeWhile_eq_take: "takeWhile P xs = take (length (takeWhile P xs)) xs"
hoelzl@33639
  1974
by (induct xs) auto
hoelzl@33639
  1975
hoelzl@33639
  1976
lemma dropWhile_eq_drop: "dropWhile P xs = drop (length (takeWhile P xs)) xs"
hoelzl@33639
  1977
by (induct xs) auto
hoelzl@33639
  1978
hoelzl@33639
  1979
lemma hd_dropWhile:
hoelzl@33639
  1980
  "dropWhile P xs \<noteq> [] \<Longrightarrow> \<not> P (hd (dropWhile P xs))"
hoelzl@33639
  1981
using assms by (induct xs) auto
hoelzl@33639
  1982
hoelzl@33639
  1983
lemma takeWhile_eq_filter:
hoelzl@33639
  1984
  assumes "\<And> x. x \<in> set (dropWhile P xs) \<Longrightarrow> \<not> P x"
hoelzl@33639
  1985
  shows "takeWhile P xs = filter P xs"
hoelzl@33639
  1986
proof -
hoelzl@33639
  1987
  have A: "filter P xs = filter P (takeWhile P xs @ dropWhile P xs)"
hoelzl@33639
  1988
    by simp
hoelzl@33639
  1989
  have B: "filter P (dropWhile P xs) = []"
hoelzl@33639
  1990
    unfolding filter_empty_conv using assms by blast
hoelzl@33639
  1991
  have "filter P xs = takeWhile P xs"
hoelzl@33639
  1992
    unfolding A filter_append B
hoelzl@33639
  1993
    by (auto simp add: filter_id_conv dest: set_takeWhileD)
hoelzl@33639
  1994
  thus ?thesis ..
hoelzl@33639
  1995
qed
hoelzl@33639
  1996
hoelzl@33639
  1997
lemma takeWhile_eq_take_P_nth:
hoelzl@33639
  1998
  "\<lbrakk> \<And> i. \<lbrakk> i < n ; i < length xs \<rbrakk> \<Longrightarrow> P (xs ! i) ; n < length xs \<Longrightarrow> \<not> P (xs ! n) \<rbrakk> \<Longrightarrow>
hoelzl@33639
  1999
  takeWhile P xs = take n xs"
hoelzl@33639
  2000
proof (induct xs arbitrary: n)
hoelzl@33639
  2001
  case (Cons x xs)
hoelzl@33639
  2002
  thus ?case
hoelzl@33639
  2003
  proof (cases n)
hoelzl@33639
  2004
    case (Suc n') note this[simp]
hoelzl@33639
  2005
    have "P x" using Cons.prems(1)[of 0] by simp
hoelzl@33639
  2006
    moreover have "takeWhile P xs = take n' xs"
hoelzl@33639
  2007
    proof (rule Cons.hyps)
hoelzl@33639
  2008
      case goal1 thus "P (xs ! i)" using Cons.prems(1)[of "Suc i"] by simp
hoelzl@33639
  2009
    next case goal2 thus ?case using Cons by auto
hoelzl@33639
  2010
    qed
hoelzl@33639
  2011
    ultimately show ?thesis by simp
hoelzl@33639
  2012
   qed simp
hoelzl@33639
  2013
qed simp
hoelzl@33639
  2014
hoelzl@33639
  2015
lemma nth_length_takeWhile:
hoelzl@33639
  2016
  "length (takeWhile P xs) < length xs \<Longrightarrow> \<not> P (xs ! length (takeWhile P xs))"
hoelzl@33639
  2017
by (induct xs) auto
hoelzl@33639
  2018
hoelzl@33639
  2019
lemma length_takeWhile_less_P_nth:
hoelzl@33639
  2020
  assumes all: "\<And> i. i < j \<Longrightarrow> P (xs ! i)" and "j \<le> length xs"
hoelzl@33639
  2021
  shows "j \<le> length (takeWhile P xs)"
hoelzl@33639
  2022
proof (rule classical)
hoelzl@33639
  2023
  assume "\<not> ?thesis"
hoelzl@33639
  2024
  hence "length (takeWhile P xs) < length xs" using assms by simp
hoelzl@33639
  2025
  thus ?thesis using all `\<not> ?thesis` nth_length_takeWhile[of P xs] by auto
hoelzl@33639
  2026
qed
nipkow@31077
  2027
nipkow@17501
  2028
text{* The following two lemmmas could be generalized to an arbitrary
nipkow@17501
  2029
property. *}
nipkow@17501
  2030
nipkow@17501
  2031
lemma takeWhile_neq_rev: "\<lbrakk>distinct xs; x \<in> set xs\<rbrakk> \<Longrightarrow>
nipkow@17501
  2032
 takeWhile (\<lambda>y. y \<noteq> x) (rev xs) = rev (tl (dropWhile (\<lambda>y. y \<noteq> x) xs))"
nipkow@17501
  2033
by(induct xs) (auto simp: takeWhile_tail[where l="[]"])
nipkow@17501
  2034
nipkow@17501
  2035
lemma dropWhile_neq_rev: "\<lbrakk>distinct xs; x \<in> set xs\<rbrakk> \<Longrightarrow>
nipkow@17501
  2036
  dropWhile (\<lambda>y. y \<noteq> x) (rev xs) = x # rev (takeWhile (\<lambda>y. y \<noteq> x) xs)"
nipkow@17501
  2037
apply(induct xs)
nipkow@17501
  2038
 apply simp
nipkow@17501
  2039
apply auto
nipkow@17501
  2040
apply(subst dropWhile_append2)
nipkow@17501
  2041
apply auto
nipkow@17501
  2042
done
nipkow@17501
  2043
nipkow@18423
  2044
lemma takeWhile_not_last:
bulwahn@46500
  2045
 "distinct xs \<Longrightarrow> takeWhile (\<lambda>y. y \<noteq> last xs) xs = butlast xs"
nipkow@18423
  2046
apply(induct xs)
nipkow@18423
  2047
 apply simp
nipkow@18423
  2048
apply(case_tac xs)
nipkow@18423
  2049
apply(auto)
nipkow@18423
  2050
done
nipkow@18423
  2051
krauss@44013
  2052
lemma takeWhile_cong [fundef_cong]:
krauss@18336
  2053
  "[| l = k; !!x. x : set l ==> P x = Q x |] 
krauss@18336
  2054
  ==> takeWhile P l = takeWhile Q k"
nipkow@24349
  2055
by (induct k arbitrary: l) (simp_all)
krauss@18336
  2056
krauss@44013
  2057
lemma dropWhile_cong [fundef_cong]:
krauss@18336
  2058
  "[| l = k; !!x. x : set l ==> P x = Q x |] 
krauss@18336
  2059
  ==> dropWhile P l = dropWhile Q k"
nipkow@24349
  2060
by (induct k arbitrary: l, simp_all)
krauss@18336
  2061
wenzelm@13114
  2062
nipkow@15392
  2063
subsubsection {* @{text zip} *}
wenzelm@13114
  2064
wenzelm@13142
  2065
lemma zip_Nil [simp]: "zip [] ys = []"
nipkow@13145
  2066
by (induct ys) auto
wenzelm@13114
  2067
wenzelm@13142
  2068
lemma zip_Cons_Cons [simp]: "zip (x # xs) (y # ys) = (x, y) # zip xs ys"
nipkow@13145
  2069
by simp
wenzelm@13114
  2070
wenzelm@13142
  2071
declare zip_Cons [simp del]
wenzelm@13114
  2072
haftmann@36198
  2073
lemma [code]:
haftmann@36198
  2074
  "zip [] ys = []"
haftmann@36198
  2075
  "zip xs [] = []"
haftmann@36198
  2076
  "zip (x # xs) (y # ys) = (x, y) # zip xs ys"
haftmann@36198
  2077
  by (fact zip_Nil zip.simps(1) zip_Cons_Cons)+
haftmann@36198
  2078
nipkow@15281
  2079
lemma zip_Cons1:
nipkow@15281
  2080
 "zip (x#xs) ys = (case ys of [] \<Rightarrow> [] | y#ys \<Rightarrow> (x,y)#zip xs ys)"
nipkow@15281
  2081
by(auto split:list.split)
nipkow@15281
  2082
wenzelm@13142
  2083
lemma length_zip [simp]:
krauss@22493
  2084
"length (zip xs ys) = min (length xs) (length ys)"
krauss@22493
  2085
by (induct xs ys rule:list_induct2') auto
wenzelm@13114
  2086
haftmann@34978
  2087
lemma zip_obtain_same_length:
haftmann@34978
  2088
  assumes "\<And>zs ws n. length zs = length ws \<Longrightarrow> n = min (length xs) (length ys)
haftmann@34978
  2089
    \<Longrightarrow> zs = take n xs \<Longrightarrow> ws = take n ys \<Longrightarrow> P (zip zs ws)"
haftmann@34978
  2090
  shows "P (zip xs ys)"
haftmann@34978
  2091
proof -
haftmann@34978
  2092
  let ?n = "min (length xs) (length ys)"
haftmann@34978
  2093
  have "P (zip (take ?n xs) (take ?n ys))"
haftmann@34978
  2094
    by (rule assms) simp_all
haftmann@34978
  2095
  moreover have "zip xs ys = zip (take ?n xs) (take ?n ys)"
haftmann@34978
  2096
  proof (induct xs arbitrary: ys)
haftmann@34978
  2097
    case Nil then show ?case by simp
haftmann@34978
  2098
  next
haftmann@34978
  2099
    case (Cons x xs) then show ?case by (cases ys) simp_all
haftmann@34978
  2100
  qed
haftmann@34978
  2101
  ultimately show ?thesis by simp
haftmann@34978
  2102
qed
haftmann@34978
  2103
wenzelm@13114
  2104
lemma zip_append1:
krauss@22493
  2105
"zip (xs @ ys) zs =
nipkow@13145
  2106
zip xs (take (length xs) zs) @ zip ys (drop (length xs) zs)"
krauss@22493
  2107
by (induct xs zs rule:list_induct2') auto
wenzelm@13114
  2108
wenzelm@13114
  2109
lemma zip_append2:
krauss@22493
  2110
"zip xs (ys @ zs) =
nipkow@13145
  2111
zip (take (length ys) xs) ys @ zip (drop (length ys) xs) zs"
krauss@22493
  2112
by (induct xs ys rule:list_induct2') auto
wenzelm@13114
  2113
wenzelm@13142
  2114
lemma zip_append [simp]:
bulwahn@46500
  2115
 "[| length xs = length us |] ==>
nipkow@13145
  2116
zip (xs@ys) (us@vs) = zip xs us @ zip ys vs"
nipkow@13145
  2117
by (simp add: zip_append1)
wenzelm@13114
  2118
wenzelm@13114
  2119
lemma zip_rev:
nipkow@14247
  2120
"length xs = length ys ==> zip (rev xs) (rev ys) = rev (zip xs ys)"
nipkow@14247
  2121
by (induct rule:list_induct2, simp_all)
wenzelm@13114
  2122
hoelzl@33639
  2123
lemma zip_map_map:
hoelzl@33639
  2124
  "zip (map f xs) (map g ys) = map (\<lambda> (x, y). (f x, g y)) (zip xs ys)"
hoelzl@33639
  2125
proof (induct xs arbitrary: ys)
hoelzl@33639
  2126
  case (Cons x xs) note Cons_x_xs = Cons.hyps
hoelzl@33639
  2127
  show ?case
hoelzl@33639
  2128
  proof (cases ys)
hoelzl@33639
  2129
    case (Cons y ys')
hoelzl@33639
  2130
    show ?thesis unfolding Cons using Cons_x_xs by simp
hoelzl@33639
  2131
  qed simp
hoelzl@33639
  2132
qed simp
hoelzl@33639
  2133
hoelzl@33639
  2134
lemma zip_map1:
hoelzl@33639
  2135
  "zip (map f xs) ys = map (\<lambda>(x, y). (f x, y)) (zip xs ys)"
hoelzl@33639
  2136
using zip_map_map[of f xs "\<lambda>x. x" ys] by simp
hoelzl@33639
  2137
hoelzl@33639
  2138
lemma zip_map2:
hoelzl@33639
  2139
  "zip xs (map f ys) = map (\<lambda>(x, y). (x, f y)) (zip xs ys)"
hoelzl@33639
  2140
using zip_map_map[of "\<lambda>x. x" xs f ys] by simp
hoelzl@33639
  2141
nipkow@23096
  2142
lemma map_zip_map:
hoelzl@33639
  2143
  "map f (zip (map g xs) ys) = map (%(x,y). f(g x, y)) (zip xs ys)"
hoelzl@33639
  2144
unfolding zip_map1 by auto
nipkow@23096
  2145
nipkow@23096
  2146
lemma map_zip_map2:
hoelzl@33639
  2147
  "map f (zip xs (map g ys)) = map (%(x,y). f(x, g y)) (zip xs ys)"
hoelzl@33639
  2148
unfolding zip_map2 by auto
nipkow@23096
  2149
nipkow@31080
  2150
text{* Courtesy of Andreas Lochbihler: *}
nipkow@31080
  2151
lemma zip_same_conv_map: "zip xs xs = map (\<lambda>x. (x, x)) xs"
nipkow@31080
  2152
by(induct xs) auto
nipkow@31080
  2153
wenzelm@13142
  2154
lemma nth_zip [simp]:
nipkow@24526
  2155
"[| i < length xs; i < length ys|] ==> (zip xs ys)!i = (xs!i, ys!i)"
nipkow@24526
  2156
apply (induct ys arbitrary: i xs, simp)
nipkow@13145
  2157
apply (case_tac xs)
nipkow@13145
  2158
 apply (simp_all add: nth.simps split: nat.split)
nipkow@13145
  2159
done
wenzelm@13114
  2160
wenzelm@13114
  2161
lemma set_zip:
nipkow@13145
  2162
"set (zip xs ys) = {(xs!i, ys!i) | i. i < min (length xs) (length ys)}"
nipkow@31080
  2163
by(simp add: set_conv_nth cong: rev_conj_cong)
wenzelm@13114
  2164
hoelzl@33639
  2165
lemma zip_same: "((a,b) \<in> set (zip xs xs)) = (a \<in> set xs \<and> a = b)"
hoelzl@33639
  2166
by(induct xs) auto
hoelzl@33639
  2167
wenzelm@13114
  2168
lemma zip_update:
nipkow@31080
  2169
  "zip (xs[i:=x]) (ys[i:=y]) = (zip xs ys)[i:=(x,y)]"
nipkow@31080
  2170
by(rule sym, simp add: update_zip)
wenzelm@13114
  2171
wenzelm@13142
  2172
lemma zip_replicate [simp]:
nipkow@24526
  2173
  "zip (replicate i x) (replicate j y) = replicate (min i j) (x,y)"
nipkow@24526
  2174
apply (induct i arbitrary: j, auto)
paulson@14208
  2175
apply (case_tac j, auto)
nipkow@13145
  2176
done
wenzelm@13114
  2177
nipkow@19487
  2178
lemma take_zip:
nipkow@24526
  2179
  "take n (zip xs ys) = zip (take n xs) (take n ys)"
nipkow@24526
  2180
apply (induct n arbitrary: xs ys)
nipkow@19487
  2181
 apply simp
nipkow@19487
  2182
apply (case_tac xs, simp)
nipkow@19487
  2183
apply (case_tac ys, simp_all)
nipkow@19487
  2184
done
nipkow@19487
  2185
nipkow@19487
  2186
lemma drop_zip:
nipkow@24526
  2187
  "drop n (zip xs ys) = zip (drop n xs) (drop n ys)"
nipkow@24526
  2188
apply (induct n arbitrary: xs ys)
nipkow@19487
  2189
 apply simp
nipkow@19487
  2190
apply (case_tac xs, simp)
nipkow@19487
  2191
apply (case_tac ys, simp_all)
nipkow@19487
  2192
done
nipkow@19487
  2193
hoelzl@33639
  2194
lemma zip_takeWhile_fst: "zip (takeWhile P xs) ys = takeWhile (P \<circ> fst) (zip xs ys)"
hoelzl@33639
  2195
proof (induct xs arbitrary: ys)
hoelzl@33639
  2196
  case (Cons x xs) thus ?case by (cases ys) auto
hoelzl@33639
  2197
qed simp
hoelzl@33639
  2198
hoelzl@33639
  2199
lemma zip_takeWhile_snd: "zip xs (takeWhile P ys) = takeWhile (P \<circ> snd) (zip xs ys)"
hoelzl@33639
  2200
proof (induct xs arbitrary: ys)
hoelzl@33639
  2201
  case (Cons x xs) thus ?case by (cases ys) auto
hoelzl@33639
  2202
qed simp
hoelzl@33639
  2203
krauss@22493
  2204
lemma set_zip_leftD:
krauss@22493
  2205
  "(x,y)\<in> set (zip xs ys) \<Longrightarrow> x \<in> set xs"
krauss@22493
  2206
by (induct xs ys rule:list_induct2') auto
krauss@22493
  2207
krauss@22493
  2208
lemma set_zip_rightD:
krauss@22493
  2209
  "(x,y)\<in> set (zip xs ys) \<Longrightarrow> y \<in> set ys"
krauss@22493
  2210
by (induct xs ys rule:list_induct2') auto
wenzelm@13142
  2211
nipkow@23983
  2212
lemma in_set_zipE:
nipkow@23983
  2213
  "(x,y) : set(zip xs ys) \<Longrightarrow> (\<lbrakk> x : set xs; y : set ys \<rbrakk> \<Longrightarrow> R) \<Longrightarrow> R"
nipkow@23983
  2214
by(blast dest: set_zip_leftD set_zip_rightD)
nipkow@23983
  2215
haftmann@29829
  2216
lemma zip_map_fst_snd:
haftmann@29829
  2217
  "zip (map fst zs) (map snd zs) = zs"
haftmann@29829
  2218
  by (induct zs) simp_all
haftmann@29829
  2219
haftmann@29829
  2220
lemma zip_eq_conv:
haftmann@29829
  2221
  "length xs = length ys \<Longrightarrow> zip xs ys = zs \<longleftrightarrow> map fst zs = xs \<and> map snd zs = ys"
haftmann@29829
  2222
  by (auto simp add: zip_map_fst_snd)
haftmann@29829
  2223
wenzelm@35115
  2224
nipkow@15392
  2225
subsubsection {* @{text list_all2} *}
wenzelm@13114
  2226
kleing@14316
  2227
lemma list_all2_lengthD [intro?]: 
kleing@14316
  2228
  "list_all2 P xs ys ==> length xs = length ys"
nipkow@24349
  2229
by (simp add: list_all2_def)
haftmann@19607
  2230
haftmann@19787
  2231
lemma list_all2_Nil [iff, code]: "list_all2 P [] ys = (ys = [])"
nipkow@24349
  2232
by (simp add: list_all2_def)
haftmann@19607
  2233
haftmann@19787
  2234
lemma list_all2_Nil2 [iff, code]: "list_all2 P xs [] = (xs = [])"
nipkow@24349
  2235
by (simp add: list_all2_def)
haftmann@19607
  2236
haftmann@19607
  2237
lemma list_all2_Cons [iff, code]:
haftmann@19607
  2238
  "list_all2 P (x # xs) (y # ys) = (P x y \<and> list_all2 P xs ys)"
nipkow@24349
  2239
by (auto simp add: list_all2_def)
wenzelm@13114
  2240
wenzelm@13114
  2241
lemma list_all2_Cons1:
nipkow@13145
  2242
"list_all2 P (x # xs) ys = (\<exists>z zs. ys = z # zs \<and> P x z \<and> list_all2 P xs zs)"
nipkow@13145
  2243
by (cases ys) auto
wenzelm@13114
  2244
wenzelm@13114
  2245
lemma list_all2_Cons2:
nipkow@13145
  2246
"list_all2 P xs (y # ys) = (\<exists>z zs. xs = z # zs \<and> P z y \<and> list_all2 P zs ys)"
nipkow@13145
  2247
by (cases xs) auto
wenzelm@13114
  2248
huffman@45794
  2249
lemma list_all2_induct
huffman@45794
  2250
  [consumes 1, case_names Nil Cons, induct set: list_all2]:
huffman@45794
  2251
  assumes P: "list_all2 P xs ys"
huffman@45794
  2252
  assumes Nil: "R [] []"
huffman@45794
  2253
  assumes Cons: "\<And>x xs y ys. \<lbrakk>P x y; R xs ys\<rbrakk> \<Longrightarrow> R (x # xs) (y # ys)"
huffman@45794
  2254
  shows "R xs ys"
huffman@45794
  2255
using P
huffman@45794
  2256
by (induct xs arbitrary: ys) (auto simp add: list_all2_Cons1 Nil Cons)
huffman@45794
  2257
wenzelm@13142
  2258
lemma list_all2_rev [iff]:
nipkow@13145
  2259
"list_all2 P (rev xs) (rev ys) = list_all2 P xs ys"
nipkow@13145
  2260
by (simp add: list_all2_def zip_rev cong: conj_cong)
wenzelm@13114
  2261
kleing@13863
  2262
lemma list_all2_rev1:
kleing@13863
  2263
"list_all2 P (rev xs) ys = list_all2 P xs (rev ys)"
kleing@13863
  2264
by (subst list_all2_rev [symmetric]) simp
kleing@13863
  2265
wenzelm@13114
  2266
lemma list_all2_append1:
nipkow@13145
  2267
"list_all2 P (xs @ ys) zs =
nipkow@13145
  2268
(EX us vs. zs = us @ vs \<and> length us = length xs \<and> length vs = length ys \<and>
nipkow@13145
  2269
list_all2 P xs us \<and> list_all2 P ys vs)"
nipkow@13145
  2270
apply (simp add: list_all2_def zip_append1)
nipkow@13145
  2271
apply (rule iffI)
nipkow@13145
  2272
 apply (rule_tac x = "take (length xs) zs" in exI)
nipkow@13145
  2273
 apply (rule_tac x = "drop (length xs) zs" in exI)
paulson@14208
  2274
 apply (force split: nat_diff_split simp add: min_def, clarify)
nipkow@13145
  2275
apply (simp add: ball_Un)
nipkow@13145
  2276
done
wenzelm@13114
  2277
wenzelm@13114
  2278
lemma list_all2_append2:
nipkow@13145
  2279
"list_all2 P xs (ys @ zs) =
nipkow@13145
  2280
(EX us vs. xs = us @ vs \<and> length us = length ys \<and> length vs = length zs \<and>
nipkow@13145
  2281
list_all2 P us ys \<and> list_all2 P vs zs)"
nipkow@13145
  2282
apply (simp add: list_all2_def zip_append2)
nipkow@13145
  2283
apply (rule iffI)
nipkow@13145
  2284
 apply (rule_tac x = "take (length ys) xs" in exI)
nipkow@13145
  2285
 apply (rule_tac x = "drop (length ys) xs" in exI)
paulson@14208
  2286
 apply (force split: nat_diff_split simp add: min_def, clarify)
nipkow@13145
  2287
apply (simp add: ball_Un)
nipkow@13145
  2288
done
wenzelm@13114
  2289
kleing@13863
  2290
lemma list_all2_append:
nipkow@14247
  2291
  "length xs = length ys \<Longrightarrow>
nipkow@14247
  2292
  list_all2 P (xs@us) (ys@vs) = (list_all2 P xs ys \<and> list_all2 P us vs)"
nipkow@14247
  2293
by (induct rule:list_induct2, simp_all)
kleing@13863
  2294
kleing@13863
  2295
lemma list_all2_appendI [intro?, trans]:
kleing@13863
  2296
  "\<lbrakk> list_all2 P a b; list_all2 P c d \<rbrakk> \<Longrightarrow> list_all2 P (a@c) (b@d)"
nipkow@24349
  2297
by (simp add: list_all2_append list_all2_lengthD)
kleing@13863
  2298
wenzelm@13114
  2299
lemma list_all2_conv_all_nth:
nipkow@13145
  2300
"list_all2 P xs ys =
nipkow@13145
  2301
(length xs = length ys \<and> (\<forall>i < length xs. P (xs!i) (ys!i)))"
nipkow@13145
  2302
by (force simp add: list_all2_def set_zip)
wenzelm@13114
  2303
berghofe@13883
  2304
lemma list_all2_trans:
berghofe@13883
  2305
  assumes tr: "!!a b c. P1 a b ==> P2 b c ==> P3 a c"
berghofe@13883
  2306
  shows "!!bs cs. list_all2 P1 as bs ==> list_all2 P2 bs cs ==> list_all2 P3 as cs"
berghofe@13883
  2307
        (is "!!bs cs. PROP ?Q as bs cs")
berghofe@13883
  2308
proof (induct as)
berghofe@13883
  2309
  fix x xs bs assume I1: "!!bs cs. PROP ?Q xs bs cs"
berghofe@13883
  2310
  show "!!cs. PROP ?Q (x # xs) bs cs"
berghofe@13883
  2311
  proof (induct bs)
berghofe@13883
  2312
    fix y ys cs assume I2: "!!cs. PROP ?Q (x # xs) ys cs"
berghofe@13883
  2313
    show "PROP ?Q (x # xs) (y # ys) cs"
berghofe@13883
  2314
      by (induct cs) (auto intro: tr I1 I2)
berghofe@13883
  2315
  qed simp
berghofe@13883
  2316
qed simp
berghofe@13883
  2317
kleing@13863
  2318
lemma list_all2_all_nthI [intro?]:
kleing@13863
  2319
  "length a = length b \<Longrightarrow> (\<And>n. n < length a \<Longrightarrow> P (a!n) (b!n)) \<Longrightarrow> list_all2 P a b"
nipkow@24349
  2320
by (simp add: list_all2_conv_all_nth)
kleing@13863
  2321
paulson@14395
  2322
lemma list_all2I:
paulson@14395
  2323
  "\<forall>x \<in> set (zip a b). split P x \<Longrightarrow> length a = length b \<Longrightarrow> list_all2 P a b"
nipkow@24349
  2324
by (simp add: list_all2_def)
paulson@14395
  2325
kleing@14328
  2326
lemma list_all2_nthD:
kleing@13863
  2327
  "\<lbrakk> list_all2 P xs ys; p < size xs \<rbrakk> \<Longrightarrow> P (xs!p) (ys!p)"
nipkow@24349
  2328
by (simp add: list_all2_conv_all_nth)
kleing@13863
  2329
nipkow@14302
  2330
lemma list_all2_nthD2:
nipkow@14302
  2331
  "\<lbrakk>list_all2 P xs ys; p < size ys\<rbrakk> \<Longrightarrow> P (xs!p) (ys!p)"
nipkow@24349
  2332
by (frule list_all2_lengthD) (auto intro: list_all2_nthD)
nipkow@14302
  2333
kleing@13863
  2334
lemma list_all2_map1: 
kleing@13863
  2335
  "list_all2 P (map f as) bs = list_all2 (\<lambda>x y. P (f x) y) as bs"
nipkow@24349
  2336
by (simp add: list_all2_conv_all_nth)
kleing@13863
  2337
kleing@13863
  2338
lemma list_all2_map2: 
kleing@13863
  2339
  "list_all2 P as (map f bs) = list_all2 (\<lambda>x y. P x (f y)) as bs"
nipkow@24349
  2340
by (auto simp add: list_all2_conv_all_nth)
kleing@13863
  2341
kleing@14316
  2342
lemma list_all2_refl [intro?]:
kleing@13863
  2343
  "(\<And>x. P x x) \<Longrightarrow> list_all2 P xs xs"
nipkow@24349
  2344
by (simp add: list_all2_conv_all_nth)
kleing@13863
  2345
kleing@13863
  2346
lemma list_all2_update_cong:
bulwahn@46669
  2347
  "\<lbrakk> list_all2 P xs ys; P x y \<rbrakk> \<Longrightarrow> list_all2 P (xs[i:=x]) (ys[i:=y])"
bulwahn@46669
  2348
by (cases "i < length ys") (auto simp add: list_all2_conv_all_nth nth_list_update)
kleing@13863
  2349
nipkow@14302
  2350
lemma list_all2_takeI [simp,intro?]:
nipkow@24526
  2351
  "list_all2 P xs ys \<Longrightarrow> list_all2 P (take n xs) (take n ys)"
nipkow@24526
  2352
apply (induct xs arbitrary: n ys)
nipkow@24526
  2353
 apply simp
nipkow@24526
  2354
apply (clarsimp simp add: list_all2_Cons1)
nipkow@24526
  2355
apply (case_tac n)
nipkow@24526
  2356
apply auto
nipkow@24526
  2357
done
nipkow@14302
  2358
nipkow@14302
  2359
lemma list_all2_dropI [simp,intro?]:
nipkow@24526
  2360
  "list_all2 P as bs \<Longrightarrow> list_all2 P (drop n as) (drop n bs)"
nipkow@24526
  2361
apply (induct as arbitrary: n bs, simp)
nipkow@24526
  2362
apply (clarsimp simp add: list_all2_Cons1)
nipkow@24526
  2363
apply (case_tac n, simp, simp)
nipkow@24526
  2364
done
kleing@13863
  2365
kleing@14327
  2366
lemma list_all2_mono [intro?]:
nipkow@24526
  2367
  "list_all2 P xs ys \<Longrightarrow> (\<And>xs ys. P xs ys \<Longrightarrow> Q xs ys) \<Longrightarrow> list_all2 Q xs ys"
nipkow@24526
  2368
apply (induct xs arbitrary: ys, simp)
nipkow@24526
  2369
apply (case_tac ys, auto)
nipkow@24526
  2370
done
kleing@13863
  2371
haftmann@22551
  2372
lemma list_all2_eq:
haftmann@22551
  2373
  "xs = ys \<longleftrightarrow> list_all2 (op =) xs ys"
nipkow@24349
  2374
by (induct xs ys rule: list_induct2') auto
haftmann@22551
  2375
nipkow@40230
  2376
lemma list_eq_iff_zip_eq:
nipkow@40230
  2377
  "xs = ys \<longleftrightarrow> length xs = length ys \<and> (\<forall>(x,y) \<in> set (zip xs ys). x = y)"
nipkow@40230
  2378
by(auto simp add: set_zip list_all2_eq list_all2_conv_all_nth cong: conj_cong)
nipkow@40230
  2379
wenzelm@13142
  2380
haftmann@46133
  2381
subsubsection {* @{const fold} with canonical argument order *}
haftmann@46133
  2382
haftmann@46133
  2383
lemma fold_remove1_split:
haftmann@46133
  2384
  assumes f: "\<And>x y. x \<in> set xs \<Longrightarrow> y \<in> set xs \<Longrightarrow> f x \<circ> f y = f y \<circ> f x"
haftmann@46133
  2385
    and x: "x \<in> set xs"
haftmann@46133
  2386
  shows "fold f xs = fold f (remove1 x xs) \<circ> f x"
haftmann@46133
  2387
  using assms by (induct xs) (auto simp add: o_assoc [symmetric])
haftmann@46133
  2388
haftmann@46133
  2389
lemma fold_cong [fundef_cong]:
haftmann@46133
  2390
  "a = b \<Longrightarrow> xs = ys \<Longrightarrow> (\<And>x. x \<in> set xs \<Longrightarrow> f x = g x)
haftmann@46133
  2391
    \<Longrightarrow> fold f xs a = fold g ys b"
haftmann@46133
  2392
  by (induct ys arbitrary: a b xs) simp_all
haftmann@46133
  2393
haftmann@46133
  2394
lemma fold_id:
haftmann@46133
  2395
  assumes "\<And>x. x \<in> set xs \<Longrightarrow> f x = id"
haftmann@46133
  2396
  shows "fold f xs = id"
haftmann@46133
  2397
  using assms by (induct xs) simp_all
haftmann@46133
  2398
haftmann@46133
  2399
lemma fold_commute:
haftmann@46133
  2400
  assumes "\<And>x. x \<in> set xs \<Longrightarrow> h \<circ> g x = f x \<circ> h"
haftmann@46133
  2401
  shows "h \<circ> fold g xs = fold f xs \<circ> h"
haftmann@46133
  2402
  using assms by (induct xs) (simp_all add: fun_eq_iff)
haftmann@46133
  2403
haftmann@46133
  2404
lemma fold_commute_apply:
haftmann@46133
  2405
  assumes "\<And>x. x \<in> set xs \<Longrightarrow> h \<circ> g x = f x \<circ> h"
haftmann@46133
  2406
  shows "h (fold g xs s) = fold f xs (h s)"
haftmann@46133
  2407
proof -
haftmann@46133
  2408
  from assms have "h \<circ> fold g xs = fold f xs \<circ> h" by (rule fold_commute)
haftmann@46133
  2409
  then show ?thesis by (simp add: fun_eq_iff)
haftmann@37605
  2410
qed
haftmann@37605
  2411
haftmann@46133
  2412
lemma fold_invariant: 
haftmann@46133
  2413
  assumes "\<And>x. x \<in> set xs \<Longrightarrow> Q x" and "P s"
haftmann@46133
  2414
    and "\<And>x s. Q x \<Longrightarrow> P s \<Longrightarrow> P (f x s)"
haftmann@46133
  2415
  shows "P (fold f xs s)"
haftmann@34978
  2416
  using assms by (induct xs arbitrary: s) simp_all
haftmann@34978
  2417
haftmann@46133
  2418
lemma fold_append [simp]:
haftmann@46133
  2419
  "fold f (xs @ ys) = fold f ys \<circ> fold f xs"
haftmann@46133
  2420
  by (induct xs) simp_all
haftmann@46133
  2421
haftmann@46133
  2422
lemma fold_map [code_unfold]:
haftmann@46133
  2423
  "fold g (map f xs) = fold (g o f) xs"
haftmann@46133
  2424
  by (induct xs) simp_all
haftmann@46133
  2425
haftmann@46133
  2426
lemma fold_rev:
haftmann@46133
  2427
  assumes "\<And>x y. x \<in> set xs \<Longrightarrow> y \<in> set xs \<Longrightarrow> f y \<circ> f x = f x \<circ> f y"
haftmann@46133
  2428
  shows "fold f (rev xs) = fold f xs"
haftmann@46133
  2429
using assms by (induct xs) (simp_all add: fold_commute_apply fun_eq_iff)
haftmann@46133
  2430
haftmann@46133
  2431
lemma fold_Cons_rev:
haftmann@46133
  2432
  "fold Cons xs = append (rev xs)"
haftmann@46133
  2433
  by (induct xs) simp_all
haftmann@46133
  2434
haftmann@46133
  2435
lemma rev_conv_fold [code]:
haftmann@46133
  2436
  "rev xs = fold Cons xs []"
haftmann@46133
  2437
  by (simp add: fold_Cons_rev)
haftmann@46133
  2438
haftmann@46133
  2439
lemma fold_append_concat_rev:
haftmann@46133
  2440
  "fold append xss = append (concat (rev xss))"
haftmann@46133
  2441
  by (induct xss) simp_all
haftmann@46133
  2442
haftmann@46133
  2443
text {* @{const Finite_Set.fold} and @{const fold} *}
haftmann@46133
  2444
haftmann@46133
  2445
lemma (in comp_fun_commute) fold_set_fold_remdups:
haftmann@46133
  2446
  "Finite_Set.fold f y (set xs) = fold f (remdups xs) y"
haftmann@35195
  2447
  by (rule sym, induct xs arbitrary: y) (simp_all add: fold_fun_comm insert_absorb)
haftmann@35195
  2448
haftmann@46133
  2449
lemma (in comp_fun_idem) fold_set_fold:
haftmann@46133
  2450
  "Finite_Set.fold f y (set xs) = fold f xs y"
haftmann@31455
  2451
  by (rule sym, induct xs arbitrary: y) (simp_all add: fold_fun_comm)
haftmann@31455
  2452
haftmann@46133
  2453
lemma (in ab_semigroup_idem_mult) fold1_set_fold:
haftmann@32681
  2454
  assumes "xs \<noteq> []"
haftmann@46133
  2455
  shows "Finite_Set.fold1 times (set xs) = fold times (tl xs) (hd xs)"
haftmann@32681
  2456
proof -
haftmann@42871
  2457
  interpret comp_fun_idem times by (fact comp_fun_idem)
haftmann@32681
  2458
  from assms obtain y ys where xs: "xs = y # ys"
haftmann@32681
  2459
    by (cases xs) auto
haftmann@32681
  2460
  show ?thesis
haftmann@32681
  2461
  proof (cases "set ys = {}")
haftmann@32681
  2462
    case True with xs show ?thesis by simp
haftmann@32681
  2463
  next
haftmann@32681
  2464
    case False
haftmann@46034
  2465
    then have "fold1 times (insert y (set ys)) = Finite_Set.fold times y (set ys)"
haftmann@32681
  2466
      by (simp only: finite_set fold1_eq_fold_idem)
haftmann@46133
  2467
    with xs show ?thesis by (simp add: fold_set_fold mult_commute)
haftmann@32681
  2468
  qed
haftmann@32681
  2469
qed
haftmann@32681
  2470
haftmann@46147
  2471
lemma union_set_fold:
haftmann@46147
  2472
  "set xs \<union> A = fold Set.insert xs A"
haftmann@46147
  2473
proof -
haftmann@46147
  2474
  interpret comp_fun_idem Set.insert
haftmann@46147
  2475
    by (fact comp_fun_idem_insert)
haftmann@46147
  2476
  show ?thesis by (simp add: union_fold_insert fold_set_fold)
haftmann@46147
  2477
qed
haftmann@46147
  2478
haftmann@46147
  2479
lemma minus_set_fold:
haftmann@46147
  2480
  "A - set xs = fold Set.remove xs A"
haftmann@46147
  2481
proof -
haftmann@46147
  2482
  interpret comp_fun_idem Set.remove
haftmann@46147
  2483
    by (fact comp_fun_idem_remove)
haftmann@46147
  2484
  show ?thesis
haftmann@46147
  2485
    by (simp add: minus_fold_remove [of _ A] fold_set_fold)
haftmann@46147
  2486
qed
haftmann@46147
  2487
haftmann@46133
  2488
lemma (in lattice) Inf_fin_set_fold:
haftmann@46133
  2489
  "Inf_fin (set (x # xs)) = fold inf xs x"
haftmann@46133
  2490
proof -
haftmann@46133
  2491
  interpret ab_semigroup_idem_mult "inf :: 'a \<Rightarrow> 'a \<Rightarrow> 'a"
haftmann@46133
  2492
    by (fact ab_semigroup_idem_mult_inf)
haftmann@46133
  2493
  show ?thesis
haftmann@46133
  2494
    by (simp add: Inf_fin_def fold1_set_fold del: set.simps)
haftmann@46133
  2495
qed
haftmann@46133
  2496
haftmann@46133
  2497
lemma (in lattice) Sup_fin_set_fold:
haftmann@46133
  2498
  "Sup_fin (set (x # xs)) = fold sup xs x"
haftmann@46133
  2499
proof -
haftmann@46133
  2500
  interpret ab_semigroup_idem_mult "sup :: 'a \<Rightarrow> 'a \<Rightarrow> 'a"
haftmann@46133
  2501
    by (fact ab_semigroup_idem_mult_sup)
haftmann@46133
  2502
  show ?thesis
haftmann@46133
  2503
    by (simp add: Sup_fin_def fold1_set_fold del: set.simps)
haftmann@46133
  2504
qed
haftmann@46133
  2505
haftmann@46133
  2506
lemma (in linorder) Min_fin_set_fold:
haftmann@46133
  2507
  "Min (set (x # xs)) = fold min xs x"
haftmann@46133
  2508
proof -
haftmann@46133
  2509
  interpret ab_semigroup_idem_mult "min :: 'a \<Rightarrow> 'a \<Rightarrow> 'a"
haftmann@46133
  2510
    by (fact ab_semigroup_idem_mult_min)
haftmann@46133
  2511
  show ?thesis
haftmann@46133
  2512
    by (simp add: Min_def fold1_set_fold del: set.simps)
haftmann@46133
  2513
qed
haftmann@46133
  2514
haftmann@46133
  2515
lemma (in linorder) Max_fin_set_fold:
haftmann@46133
  2516
  "Max (set (x # xs)) = fold max xs x"
haftmann@46133
  2517
proof -
haftmann@46133
  2518
  interpret ab_semigroup_idem_mult "max :: 'a \<Rightarrow> 'a \<Rightarrow> 'a"
haftmann@46133
  2519
    by (fact ab_semigroup_idem_mult_max)
haftmann@46133
  2520
  show ?thesis
haftmann@46133
  2521
    by (simp add: Max_def fold1_set_fold del: set.simps)
haftmann@46133
  2522
qed
haftmann@46133
  2523
haftmann@46133
  2524
lemma (in complete_lattice) Inf_set_fold:
haftmann@46133
  2525
  "Inf (set xs) = fold inf xs top"
haftmann@46133
  2526
proof -
haftmann@46133
  2527
  interpret comp_fun_idem "inf :: 'a \<Rightarrow> 'a \<Rightarrow> 'a"
haftmann@46133
  2528
    by (fact comp_fun_idem_inf)
haftmann@46133
  2529
  show ?thesis by (simp add: Inf_fold_inf fold_set_fold inf_commute)
haftmann@46133
  2530
qed
haftmann@46133
  2531
haftmann@46133
  2532
lemma (in complete_lattice) Sup_set_fold:
haftmann@46133
  2533
  "Sup (set xs) = fold sup xs bot"
haftmann@46133
  2534
proof -
haftmann@46133
  2535
  interpret comp_fun_idem "sup :: 'a \<Rightarrow> 'a \<Rightarrow> 'a"
haftmann@46133
  2536
    by (fact comp_fun_idem_sup)
haftmann@46133
  2537
  show ?thesis by (simp add: Sup_fold_sup fold_set_fold sup_commute)
haftmann@46133
  2538
qed
haftmann@46133
  2539
haftmann@46133
  2540
lemma (in complete_lattice) INF_set_fold:
haftmann@46133
  2541
  "INFI (set xs) f = fold (inf \<circ> f) xs top"
haftmann@46133
  2542
  unfolding INF_def set_map [symmetric] Inf_set_fold fold_map ..
haftmann@46133
  2543
haftmann@46133
  2544
lemma (in complete_lattice) SUP_set_fold:
haftmann@46133
  2545
  "SUPR (set xs) f = fold (sup \<circ> f) xs bot"
haftmann@46133
  2546
  unfolding SUP_def set_map [symmetric] Sup_set_fold fold_map ..
haftmann@46133
  2547
haftmann@46133
  2548
haftmann@46133
  2549
subsubsection {* Fold variants: @{const foldr} and @{const foldl} *}
haftmann@46133
  2550
haftmann@46133
  2551
text {* Correspondence *}
haftmann@46133
  2552
haftmann@46133
  2553
lemma foldr_foldl: -- {* The ``Third Duality Theorem'' in Bird \& Wadler: *}
haftmann@46133
  2554
  "foldr f xs a = foldl (\<lambda>x y. f y x) a (rev xs)"
haftmann@46133
  2555
  by (simp add: foldr_def foldl_def)
haftmann@46133
  2556
haftmann@46133
  2557
lemma foldl_foldr:
haftmann@46133
  2558
  "foldl f a xs = foldr (\<lambda>x y. f y x) (rev xs) a"
haftmann@46133
  2559
  by (simp add: foldr_def foldl_def)
haftmann@46133
  2560
haftmann@46133
  2561
lemma foldr_fold:
haftmann@46133
  2562
  assumes "\<And>x y. x \<in> set xs \<Longrightarrow> y \<in> set xs \<Longrightarrow> f y \<circ> f x = f x \<circ> f y"
haftmann@46133
  2563
  shows "foldr f xs = fold f xs"
haftmann@46133
  2564
  using assms unfolding foldr_def by (rule fold_rev)
haftmann@46133
  2565
haftmann@46133
  2566
lemma
haftmann@46133
  2567
  foldr_Nil [code, simp]: "foldr f [] = id"
haftmann@46133
  2568
  and foldr_Cons [code, simp]: "foldr f (x # xs) = f x \<circ> foldr f xs"
haftmann@46133
  2569
  by (simp_all add: foldr_def)
haftmann@46133
  2570
haftmann@46133
  2571
lemma
haftmann@46133
  2572
  foldl_Nil [simp]: "foldl f a [] = a"
haftmann@46133
  2573
  and foldl_Cons [simp]: "foldl f a (x # xs) = foldl f (f a x) xs"
haftmann@46133
  2574
  by (simp_all add: foldl_def)
haftmann@46133
  2575
haftmann@46133
  2576
lemma foldr_cong [fundef_cong]:
haftmann@46133
  2577
  "a = b \<Longrightarrow> l = k \<Longrightarrow> (\<And>a x. x \<in> set l \<Longrightarrow> f x a = g x a) \<Longrightarrow> foldr f l a = foldr g k b"
haftmann@46133
  2578
  by (auto simp add: foldr_def intro!: fold_cong)
haftmann@46133
  2579
haftmann@46133
  2580
lemma foldl_cong [fundef_cong]:
haftmann@46133
  2581
  "a = b \<Longrightarrow> l = k \<Longrightarrow> (\<And>a x. x \<in> set l \<Longrightarrow> f a x = g a x) \<Longrightarrow> foldl f a l = foldl g b k"
haftmann@46133
  2582
  by (auto simp add: foldl_def intro!: fold_cong)
haftmann@46133
  2583
haftmann@46133
  2584
lemma foldr_append [simp]:
haftmann@46133
  2585
  "foldr f (xs @ ys) a = foldr f xs (foldr f ys a)"
haftmann@46133
  2586
  by (simp add: foldr_def)
haftmann@46133
  2587
haftmann@46133
  2588
lemma foldl_append [simp]:
haftmann@46133
  2589
  "foldl f a (xs @ ys) = foldl f (foldl f a xs) ys"
haftmann@46133
  2590
  by (simp add: foldl_def)
haftmann@46133
  2591
haftmann@46133
  2592
lemma foldr_map [code_unfold]:
haftmann@46133
  2593
  "foldr g (map f xs) a = foldr (g o f) xs a"
haftmann@46133
  2594
  by (simp add: foldr_def fold_map rev_map)
haftmann@46133
  2595
haftmann@46133
  2596
lemma foldl_map [code_unfold]:
haftmann@46133
  2597
  "foldl g a (map f xs) = foldl (\<lambda>a x. g a (f x)) a xs"
haftmann@46133
  2598
  by (simp add: foldl_def fold_map comp_def)
haftmann@46133
  2599
haftmann@46133
  2600
text {* Executing operations in terms of @{const foldr} -- tail-recursive! *}
haftmann@46133
  2601
haftmann@46133
  2602
lemma concat_conv_foldr [code]:
haftmann@46133
  2603
  "concat xss = foldr append xss []"
haftmann@46133
  2604
  by (simp add: fold_append_concat_rev foldr_def)
haftmann@46133
  2605
haftmann@46156
  2606
lemma minus_set_foldr [code]:
haftmann@46156
  2607
  "A - set xs = foldr Set.remove xs A"
haftmann@46156
  2608
proof -
haftmann@46156
  2609
  have "\<And>x y :: 'a. Set.remove y \<circ> Set.remove x = Set.remove x \<circ> Set.remove y"
haftmann@46156
  2610
    by (auto simp add: remove_def)
haftmann@46156
  2611
  then show ?thesis by (simp add: minus_set_fold foldr_fold)
haftmann@46156
  2612
qed
haftmann@46156
  2613
haftmann@46156
  2614
lemma subtract_coset_filter [code]:
haftmann@46156
  2615
  "A - List.coset xs = set (List.filter (\<lambda>x. x \<in> A) xs)"
haftmann@46156
  2616
  by auto
haftmann@46156
  2617
haftmann@46156
  2618
lemma union_set_foldr [code]:
haf