src/HOL/ex/Quickcheck.thy
 author haftmann Tue, 23 Sep 2008 18:11:42 +0200 changeset 28335 25326092cf9a parent 28315 d3cf88fe77bc child 28360 cf3542e34726 permissions -rw-r--r--
renamed rtype to typerep
```
(*  ID:         \$Id\$
Author:     Florian Haftmann, TU Muenchen
*)

header {* A simple counterexample generator *}

theory Quickcheck
imports Random Code_Eval
begin

subsection {* The @{text random} class *}

class random = typerep +
fixes random :: "index \<Rightarrow> seed \<Rightarrow> ('a \<times> (unit \<Rightarrow> term)) \<times> seed"

text {* Type @{typ "'a itself"} *}

instantiation itself :: ("{type, typerep}") random
begin

definition
"random _ = return (TYPE('a), \<lambda>u. Code_Eval.Const (STR ''TYPE'') TYPEREP('a))"

instance ..

end

text {* Datatypes *}

definition
collapse :: "('a \<Rightarrow> ('a \<Rightarrow> 'b \<times> 'a) \<times> 'a) \<Rightarrow> 'a \<Rightarrow> 'b \<times> 'a" where
"collapse f = (do g \<leftarrow> f; g done)"

ML {*
struct

fun liftT T sT = sT --> HOLogic.mk_prodT (T, sT);
fun liftT' sT = sT --> sT;

fun return T sT x = Const (@{const_name return}, T --> liftT T sT) \$ x;

fun scomp T1 T2 sT f g = Const (@{const_name scomp},
liftT T1 sT --> (T1 --> liftT T2 sT) --> liftT T2 sT) \$ f \$ g;

end;
*}

lemma random'_if:
fixes random' :: "index \<Rightarrow> index \<Rightarrow> seed \<Rightarrow> ('a \<times> (unit \<Rightarrow> term)) \<times> seed"
assumes "random' 0 j = undefined"
and "\<And>i. random' (Suc_index i) j = rhs2 i"
shows "random' i j s = (if i = 0 then undefined else rhs2 (i - 1) s)"
by (cases i rule: index.exhaust) (insert assms, simp_all add: undefined_fun)

setup {*
let
exception REC of string;
fun mk_collapse thy ty = Sign.mk_const thy
(@{const_name collapse}, [@{typ seed}, ty]);
fun term_ty ty = HOLogic.mk_prodT (ty, @{typ "unit \<Rightarrow> term"});
fun mk_split thy ty ty' = Sign.mk_const thy
(@{const_name split}, [ty, @{typ "unit \<Rightarrow> term"}, StateMonad.liftT (term_ty ty') @{typ seed}]);
fun mk_scomp_split thy ty ty' t t' =
StateMonad.scomp (term_ty ty) (term_ty ty') @{typ seed} t
(mk_split thy ty ty' \$ Abs ("", ty, Abs ("", @{typ "unit \<Rightarrow> term"}, t')))
fun mk_cons thy this_ty (c, args) =
let
val tys = map (fst o fst) args;
val c_ty = tys ---> this_ty;
val c = Const (c, tys ---> this_ty);
val t_indices = map (curry ( op * ) 2) (length tys - 1 downto 0);
val c_indices = map (curry ( op + ) 1) t_indices;
val c_t = list_comb (c, map Bound c_indices);
val t_t = Abs ("", @{typ unit}, Eval.mk_term Free Typerep.typerep
(list_comb (c, map (fn k => Bound (k + 1)) t_indices))
|> map_aterms (fn t as Bound _ => t \$ @{term "()"} | t => t));
val return = StateMonad.return (term_ty this_ty) @{typ seed}
(HOLogic.mk_prod (c_t, t_t));
val t = fold_rev (fn ((ty, _), random) =>
mk_scomp_split thy ty this_ty random)
args return;
val is_rec = exists (snd o fst) args;
in (is_rec, t) end;
fun mk_conss thy ty [] = NONE
| mk_conss thy ty [(_, t)] = SOME t
| mk_conss thy ty ts = SOME (mk_collapse thy (term_ty ty) \$
(Sign.mk_const thy (@{const_name select}, [StateMonad.liftT (term_ty ty) @{typ seed}]) \$
HOLogic.mk_list (StateMonad.liftT (term_ty ty) @{typ seed}) (map snd ts)));
fun mk_clauses thy ty (tyco, (ts_rec, ts_atom)) =
let
val SOME t_atom = mk_conss thy ty ts_atom;
in case mk_conss thy ty ts_rec
of SOME t_rec => mk_collapse thy (term_ty ty) \$
(Sign.mk_const thy (@{const_name select_default}, [StateMonad.liftT (term_ty ty) @{typ seed}]) \$
@{term "i\<Colon>index"} \$ t_rec \$ t_atom)
| NONE => t_atom
end;
fun mk_random_eqs thy vs tycos =
let
val this_ty = Type (hd tycos, map TFree vs);
val this_ty' = StateMonad.liftT (term_ty this_ty) @{typ seed};
val random_name = NameSpace.base @{const_name random};
val random'_name = random_name ^ "_" ^ Class.type_name (hd tycos) ^ "'";
fun random ty = Sign.mk_const thy (@{const_name random}, [ty]);
val random' = Free (random'_name,
@{typ index} --> @{typ index} --> this_ty');
fun atom ty = ((ty, false), random ty \$ @{term "j\<Colon>index"});
fun dtyp tyco = ((this_ty, true), random' \$ @{term "i\<Colon>index"} \$ @{term "j\<Colon>index"});
fun rtyp tyco tys = raise REC
("Will not generate random elements for mutual recursive type " ^ quote (hd tycos));
val rhss = DatatypePackage.construction_interpretation thy
{ atom = atom, dtyp = dtyp, rtyp = rtyp } vs tycos
|> (map o apsnd o map) (mk_cons thy this_ty)
|> (map o apsnd) (List.partition fst)
|> map (mk_clauses thy this_ty)
val eqss = map ((apsnd o map) (HOLogic.mk_Trueprop o HOLogic.mk_eq) o (fn rhs => ((this_ty, random'), [
(random' \$ @{term "0\<Colon>index"} \$ @{term "j\<Colon>index"}, Const (@{const_name undefined}, this_ty')),
(random' \$ @{term "Suc_index i"} \$ @{term "j\<Colon>index"}, rhs)
]))) rhss;
in eqss end;
fun random_inst [tyco] thy =
let
val (raw_vs, _) = DatatypePackage.the_datatype_spec thy tyco;
val vs = (map o apsnd)
(curry (Sorts.inter_sort (Sign.classes_of thy)) @{sort random}) raw_vs;
val { descr, index, ... } = DatatypePackage.the_datatype thy tyco;
val ((this_ty, random'), eqs') = singleton (mk_random_eqs thy vs) tyco;
val eq = (HOLogic.mk_Trueprop o HOLogic.mk_eq)
(Sign.mk_const thy (@{const_name random}, [this_ty]) \$ @{term "i\<Colon>index"},
random' \$ @{term "i\<Colon>index"} \$ @{term "i\<Colon>index"})
val del_func = Attrib.internal (fn _ => Thm.declaration_attribute
(fn thm => Context.mapping (Code.del_func thm) I));
let
val thy = ProofContext.theory_of lthy;
val thm = @{thm random'_if}
|> Drule.instantiate' [SOME (Thm.ctyp_of thy this_ty)] [SOME (Thm.cterm_of thy random')]
|> (fn thm => thm OF simps)
|> singleton (ProofContext.export lthy (ProofContext.init thy))
in
lthy
|> LocalTheory.theory (PureThy.add_thm ((fst (dest_Free random') ^ "_code", thm), [Thm.kind_internal])
end;
in
thy
|> TheoryTarget.instantiation ([tyco], vs, @{sort random})
[(Name.binding (fst (dest_Free random')), SOME (snd (dest_Free random')), NoSyn)]
(map (fn eq => ((Name.no_binding, [del_func]), eq)) eqs')
|> `(fn lthy => Syntax.check_term lthy eq)
|-> (fn eq => Specification.definition (NONE, (Attrib.no_binding, eq)))
|> snd
|> Class.prove_instantiation_instance (K (Class.intro_classes_tac []))
|> LocalTheory.exit
|> ProofContext.theory_of
end
| random_inst tycos thy = raise REC
("Will not generate random elements for mutual recursive type(s) " ^ commas (map quote tycos));
fun add_random_inst tycos thy = random_inst tycos thy
handle REC msg => (warning msg; thy);
*}

text {* Type @{typ int} *}

instantiation int :: random
begin

definition
"random n = (do
(b, _) \<leftarrow> random n;
(m, t) \<leftarrow> random n;
return (if b then (int m, \<lambda>u. Code_Eval.App (Code_Eval.Const (STR ''Int.int'') TYPEREP(nat \<Rightarrow> int)) (t ()))
else (- int m, \<lambda>u. Code_Eval.App (Code_Eval.Const (STR ''HOL.uminus_class.uminus'') TYPEREP(int \<Rightarrow> int))
(Code_Eval.App (Code_Eval.Const (STR ''Int.int'') TYPEREP(nat \<Rightarrow> int)) (t ()))))
done)"

instance ..

end

text {* Type @{typ "'a \<Rightarrow> 'b"} *}

ML {*
structure Random_Engine =
struct

open Random_Engine;

fun random_fun (T1 : typ) (T2 : typ) (eq : 'a -> 'a -> bool) (term_of : 'a -> term)
(random : Random_Engine.seed -> ('b * (unit -> term)) * Random_Engine.seed)
(random_split : Random_Engine.seed -> Random_Engine.seed * Random_Engine.seed)
(seed : Random_Engine.seed) =
let
val (seed', seed'') = random_split seed;
val state = ref (seed', [], Const (@{const_name arbitrary}, T1 --> T2));
val fun_upd = Const (@{const_name fun_upd},
(T1 --> T2) --> T1 --> T2 --> T1 --> T2);
fun random_fun' x =
let
val (seed, fun_map, f_t) = ! state;
in case AList.lookup (uncurry eq) fun_map x
of SOME y => y
| NONE => let
val t1 = term_of x;
val ((y, t2), seed') = random seed;
val fun_map' = (x, y) :: fun_map;
val f_t' = fun_upd \$ f_t \$ t1 \$ t2 ();
val _ = state := (seed', fun_map', f_t');
in y end
end;
fun term_fun' () = #3 (! state);
in ((random_fun', term_fun'), seed'') end;

end
*}

axiomatization
random_fun_aux :: "typerep \<Rightarrow> typerep \<Rightarrow> ('a \<Rightarrow> 'a \<Rightarrow> bool) \<Rightarrow> ('a \<Rightarrow> term)
\<Rightarrow> (seed \<Rightarrow> ('b \<times> (unit \<Rightarrow> term)) \<times> seed) \<Rightarrow> (seed \<Rightarrow> seed \<times> seed)
\<Rightarrow> seed \<Rightarrow> (('a \<Rightarrow> 'b) \<times> (unit \<Rightarrow> term)) \<times> seed"

code_const random_fun_aux (SML "Random'_Engine.random'_fun")

instantiation "fun" :: ("{eq, term_of}", "{type, random}") random
begin

definition random_fun :: "index \<Rightarrow> seed \<Rightarrow> (('a \<Rightarrow> 'b) \<times> (unit \<Rightarrow> term)) \<times> seed" where
"random n = random_fun_aux TYPEREP('a) TYPEREP('b) (op =) Code_Eval.term_of (random n) split_seed"

instance ..

end

code_reserved SML Random_Engine

subsection {* Quickcheck generator *}

ML {*
structure Quickcheck =
struct

open Quickcheck;

val eval_ref : (unit -> int -> int * int -> term list option * (int * int)) option ref = ref NONE;

fun mk_generator_expr thy prop tys =
let
val bound_max = length tys - 1;
val bounds = map_index (fn (i, ty) =>
(2 * (bound_max - i) + 1, 2 * (bound_max - i), 2 * i, ty)) tys;
val result = list_comb (prop, map (fn (i, _, _, _) => Bound i) bounds);
val terms = HOLogic.mk_list @{typ term} (map (fn (_, i, _, _) => Bound i \$ @{term "()"}) bounds);
val check = @{term "If \<Colon> bool \<Rightarrow> term list option \<Rightarrow> term list option \<Rightarrow> term list option"}
\$ result \$ @{term "None \<Colon> term list option"} \$ (@{term "Some \<Colon> term list \<Rightarrow> term list option "} \$ terms);
val return = @{term "Pair \<Colon> term list option \<Rightarrow> seed \<Rightarrow> term list option \<times> seed"};
fun mk_termtyp ty = HOLogic.mk_prodT (ty, @{typ "unit \<Rightarrow> term"});
fun mk_split ty = Sign.mk_const thy
(@{const_name split}, [ty, @{typ "unit \<Rightarrow> term"}, StateMonad.liftT @{typ "term list option"} @{typ seed}]);
fun mk_scomp_split ty t t' =
StateMonad.scomp (mk_termtyp ty) @{typ "term list option"} @{typ seed} t (*FIXME*)
(mk_split ty \$ Abs ("", ty, Abs ("", @{typ "unit \<Rightarrow> term"}, t')));
fun mk_bindclause (_, _, i, ty) = mk_scomp_split ty
(Sign.mk_const thy (@{const_name random}, [ty]) \$ Bound i)
val t = fold_rev mk_bindclause bounds (return \$ check);
in Abs ("n", @{typ index}, t) end;

fun compile_generator_expr thy t =
let
val tys = (map snd o fst o strip_abs) t;
val t' = mk_generator_expr thy t tys;
val f = Code_ML.eval_term ("Quickcheck.eval_ref", eval_ref) thy t' [];
in f #> Random_Engine.run #> (Option.map o map) (Code.postprocess_term thy) end;

end
*}

setup {*
*}

subsection {* Examples *}

theorem "map g (map f xs) = map (g o f) xs"
quickcheck [generator = code]
by (induct xs) simp_all

theorem "map g (map f xs) = map (f o g) xs"
quickcheck [generator = code]
oops

theorem "rev (xs @ ys) = rev ys @ rev xs"
quickcheck [generator = code]
by simp

theorem "rev (xs @ ys) = rev xs @ rev ys"
quickcheck [generator = code]
oops

theorem "rev (rev xs) = xs"
quickcheck [generator = code]
by simp

theorem "rev xs = xs"
quickcheck [generator = code]
oops

primrec app :: "('a \<Rightarrow> 'a) list \<Rightarrow> 'a \<Rightarrow> 'a" where
"app [] x = x"
| "app (f # fs) x = app fs (f x)"

lemma "app (fs @ gs) x = app gs (app fs x)"
quickcheck [generator = code]
by (induct fs arbitrary: x) simp_all

lemma "app (fs @ gs) x = app fs (app gs x)"
quickcheck [generator = code]
oops

primrec occurs :: "'a \<Rightarrow> 'a list \<Rightarrow> nat" where
"occurs a [] = 0"
| "occurs a (x#xs) = (if (x=a) then Suc(occurs a xs) else occurs a xs)"

primrec del1 :: "'a \<Rightarrow> 'a list \<Rightarrow> 'a list" where
"del1 a [] = []"
| "del1 a (x#xs) = (if (x=a) then xs else (x#del1 a xs))"

lemma "Suc (occurs a (del1 a xs)) = occurs a xs"
-- {* Wrong. Precondition needed.*}
quickcheck [generator = code]
oops

lemma "xs ~= [] \<longrightarrow> Suc (occurs a (del1 a xs)) = occurs a xs"
quickcheck [generator = code]
-- {* Also wrong.*}
oops

lemma "0 < occurs a xs \<longrightarrow> Suc (occurs a (del1 a xs)) = occurs a xs"
quickcheck [generator = code]
by (induct xs) auto

primrec replace :: "'a \<Rightarrow> 'a \<Rightarrow> 'a list \<Rightarrow> 'a list" where
"replace a b [] = []"
| "replace a b (x#xs) = (if (x=a) then (b#(replace a b xs))
else (x#(replace a b xs)))"

lemma "occurs a xs = occurs b (replace a b xs)"
quickcheck [generator = code]
-- {* Wrong. Precondition needed.*}
oops

lemma "occurs b xs = 0 \<or> a=b \<longrightarrow> occurs a xs = occurs b (replace a b xs)"
quickcheck [generator = code]
by (induct xs) simp_all

subsection {* Trees *}

datatype 'a tree = Twig |  Leaf 'a | Branch "'a tree" "'a tree"

primrec leaves :: "'a tree \<Rightarrow> 'a list" where
"leaves Twig = []"
| "leaves (Leaf a) = [a]"
| "leaves (Branch l r) = (leaves l) @ (leaves r)"

primrec plant :: "'a list \<Rightarrow> 'a tree" where
"plant [] = Twig "
| "plant (x#xs) = Branch (Leaf x) (plant xs)"

primrec mirror :: "'a tree \<Rightarrow> 'a tree" where
"mirror (Twig) = Twig "
| "mirror (Leaf a) = Leaf a "
| "mirror (Branch l r) = Branch (mirror r) (mirror l)"

theorem "plant (rev (leaves xt)) = mirror xt"
quickcheck [generator = code]
--{* Wrong! *}
oops

theorem "plant (leaves xt @ leaves yt) = Branch xt yt"
quickcheck [generator = code]
--{* Wrong! *}
oops

datatype 'a ntree = Tip "'a" | Node "'a" "'a ntree" "'a ntree"

primrec inOrder :: "'a ntree \<Rightarrow> 'a list" where
"inOrder (Tip a)= [a]"
| "inOrder (Node f x y) = (inOrder x)@[f]@(inOrder y)"

primrec root :: "'a ntree \<Rightarrow> 'a" where
"root (Tip a) = a"
| "root (Node f x y) = f"

theorem "hd (inOrder xt) = root xt"
quickcheck [generator = code]
--{* Wrong! *}
oops

lemma "int (f k) = k"
quickcheck [generator = code]
oops

end
```