src/Pure/library.ML
author wenzelm
Tue Jul 22 19:33:52 1997 +0200 (1997-07-22)
changeset 3553 a148c7e7152e
parent 3525 88edd3450460
child 3606 5d7073700fbc
permissions -rw-r--r--
added error_msg;
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(*  Title:      Pure/library.ML
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1992  University of Cambridge
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Basic library: functions, options, pairs, booleans, lists, integers,
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strings, lists as sets, association lists, generic tables, balanced trees,
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orders, input / output, timing, filenames, misc functions.
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*)
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infix |> ~~ \ \\ orelf ins ins_string ins_int orf andf prefix upto downto
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      mem mem_int mem_string union union_int union_string  
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      inter inter_int inter_string subset subset_int subset_string subdir_of;
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structure Library =
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struct
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(** functions **)
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(*handy combinators*)
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fun curry f x y = f (x, y);
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fun uncurry f (x, y) = f x y;
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fun I x = x;
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fun K x y = x;
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(*reverse apply*)
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fun (x |> f) = f x;
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(*combine two functions forming the union of their domains*)
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fun (f orelf g) = fn x => f x handle Match => g x;
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(*application of (infix) operator to its left or right argument*)
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fun apl (x, f) y = f (x, y);
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fun apr (f, y) x = f (x, y);
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(*functional for pairs*)
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fun pairself f (x, y) = (f x, f y);
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(*function exponentiation: f(...(f x)...) with n applications of f*)
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fun funpow n f x =
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  let fun rep (0, x) = x
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        | rep (n, x) = rep (n - 1, f x)
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  in rep (n, x) end;
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(** stamps **)
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type stamp = unit ref;
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val stamp: unit -> stamp = ref;
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(** options **)
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datatype 'a option = None | Some of 'a;
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exception OPTION of string;
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fun the (Some x) = x
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  | the None = raise OPTION "the";
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fun if_none None y = y
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  | if_none (Some x) _ = x;
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fun is_some (Some _) = true
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  | is_some None = false;
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fun is_none (Some _) = false
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  | is_none None = true;
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fun apsome f (Some x) = Some (f x)
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  | apsome _ None = None;
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(** pairs **)
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fun pair x y = (x, y);
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fun rpair x y = (y, x);
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fun fst (x, y) = x;
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fun snd (x, y) = y;
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fun eq_fst ((x1, _), (x2, _)) = x1 = x2;
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fun eq_snd ((_, y1), (_, y2)) = y1 = y2;
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fun swap (x, y) = (y, x);
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(*apply the function to a component of a pair*)
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fun apfst f (x, y) = (f x, y);
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fun apsnd f (x, y) = (x, f y);
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(** booleans **)
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(* equality *)
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fun equal x y = x = y;
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fun not_equal x y = x <> y;
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(* operators for combining predicates *)
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fun (p orf q) = fn x => p x orelse q x;
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fun (p andf q) = fn x => p x andalso q x;
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fun notf p x = not (p x);
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(* predicates on lists *)
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fun orl [] = false
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  | orl (x :: xs) = x orelse orl xs;
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fun andl [] = true
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  | andl (x :: xs) = x andalso andl xs;
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(*Several object-logics declare theories named List or Option, hiding the
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  eponymous basis library structures.*)
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structure List_ = List
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and       Option_ = Option;
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(*exists pred [x1, ..., xn] ===> pred x1 orelse ... orelse pred xn*)
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fun exists (pred: 'a -> bool) : 'a list -> bool =
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  let fun boolf [] = false
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        | boolf (x :: xs) = pred x orelse boolf xs
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  in boolf end;
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(*forall pred [x1, ..., xn] ===> pred x1 andalso ... andalso pred xn*)
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fun forall (pred: 'a -> bool) : 'a list -> bool =
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  let fun boolf [] = true
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        | boolf (x :: xs) = pred x andalso boolf xs
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  in boolf end;
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(* flags *)
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fun set flag = (flag := true; true);
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fun reset flag = (flag := false; false);
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fun toggle flag = (flag := not (! flag); ! flag);
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fun setmp flag value f x =
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  let
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    val orig_value = ! flag;
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    fun return y = (flag := orig_value; y);
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  in
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    flag := value;
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    return (f x handle exn => (return (); raise exn))
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  end;
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(** lists **)
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exception LIST of string;
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fun null [] = true
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  | null (_ :: _) = false;
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fun hd [] = raise LIST "hd"
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  | hd (x :: _) = x;
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fun tl [] = raise LIST "tl"
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  | tl (_ :: xs) = xs;
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fun cons x xs = x :: xs;
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(* fold *)
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(*the following versions of fold are designed to fit nicely with infixes*)
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(*  (op @) (e, [x1, ..., xn])  ===>  ((e @ x1) @ x2) ... @ xn
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    for operators that associate to the left (TAIL RECURSIVE)*)
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fun foldl (f: 'a * 'b -> 'a) : 'a * 'b list -> 'a =
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  let fun itl (e, [])  = e
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        | itl (e, a::l) = itl (f(e, a), l)
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  in  itl end;
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(*  (op @) ([x1, ..., xn], e)  ===>   x1 @ (x2 ... @ (xn @ e))
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    for operators that associate to the right (not tail recursive)*)
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fun foldr f (l, e) =
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  let fun itr [] = e
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        | itr (a::l) = f(a, itr l)
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  in  itr l  end;
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(*  (op @) [x1, ..., xn]  ===>   x1 @ (x2 ... @ (x[n-1] @ xn))
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    for n > 0, operators that associate to the right (not tail recursive)*)
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fun foldr1 f l =
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  let fun itr [x] = x                       (* FIXME [] case: elim warn (?) *)
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        | itr (x::l) = f(x, itr l)
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  in  itr l  end;
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(* basic list functions *)
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(*length of a list, should unquestionably be a standard function*)
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local fun length1 (n, [])  = n   (*TAIL RECURSIVE*)
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        | length1 (n, x :: xs) = length1 (n + 1, xs)
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in  fun length l = length1 (0, l) end;
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(*take the first n elements from a list*)
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fun take (n, []) = []
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  | take (n, x :: xs) =
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      if n > 0 then x :: take (n - 1, xs) else [];
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(*drop the first n elements from a list*)
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fun drop (n, []) = []
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  | drop (n, x :: xs) =
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      if n > 0 then drop (n - 1, xs) else x :: xs;
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(*return nth element of a list, where 0 designates the first element;
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  raise EXCEPTION if list too short*)
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fun nth_elem NL =
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  (case drop NL of
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    [] => raise LIST "nth_elem"
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  | x :: _ => x);
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(*last element of a list*)
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fun last_elem [] = raise LIST "last_elem"
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  | last_elem [x] = x
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  | last_elem (_ :: xs) = last_elem xs;
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(*find the position of an element in a list*)
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fun find (x, ys) =
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  let fun f (y :: ys, i) = if x = y then i else f (ys, i + 1)
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        | f (_, _) = raise LIST "find"
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  in f (ys, 0) end;
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(*flatten a list of lists to a list*)
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fun flat (ls: 'c list list) : 'c list = foldr (op @) (ls, []);
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(*like Lisp's MAPC -- seq proc [x1, ..., xn] evaluates
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  (proc x1; ...; proc xn) for side effects*)
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fun seq (proc: 'a -> unit) : 'a list -> unit =
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  let fun seqf [] = ()
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        | seqf (x :: xs) = (proc x; seqf xs)
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  in seqf end;
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(*separate s [x1, x2, ..., xn]  ===>  [x1, s, x2, s, ..., s, xn]*)
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fun separate s (x :: (xs as _ :: _)) = x :: s :: separate s xs
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  | separate _ xs = xs;
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(*make the list [x, x, ..., x] of length n*)
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fun replicate n (x: 'a) : 'a list =
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  let fun rep (0, xs) = xs
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        | rep (n, xs) = rep (n - 1, x :: xs)
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  in
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    if n < 0 then raise LIST "replicate"
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    else rep (n, [])
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  end;
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(* filter *)
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(*copy the list preserving elements that satisfy the predicate*)
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fun filter (pred: 'a->bool) : 'a list -> 'a list =
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  let fun filt [] = []
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        | filt (x :: xs) = if pred x then x :: filt xs else filt xs
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  in filt end;
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fun filter_out f = filter (not o f);
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fun mapfilter (f: 'a -> 'b option) ([]: 'a list) = [] : 'b list
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  | mapfilter f (x :: xs) =
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      (case f x of
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        None => mapfilter f xs
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      | Some y => y :: mapfilter f xs);
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fun find_first _ [] = None
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  | find_first pred (x :: xs) =
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      if pred x then Some x else find_first pred xs;
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(* lists of pairs *)
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fun map2 _ ([], []) = []
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  | map2 f (x :: xs, y :: ys) = (f (x, y) :: map2 f (xs, ys))
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  | map2 _ _ = raise LIST "map2";
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fun exists2 _ ([], []) = false
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  | exists2 pred (x :: xs, y :: ys) = pred (x, y) orelse exists2 pred (xs, ys)
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  | exists2 _ _ = raise LIST "exists2";
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fun forall2 _ ([], []) = true
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  | forall2 pred (x :: xs, y :: ys) = pred (x, y) andalso forall2 pred (xs, ys)
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  | forall2 _ _ = raise LIST "forall2";
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(*combine two lists forming a list of pairs:
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  [x1, ..., xn] ~~ [y1, ..., yn]  ===>  [(x1, y1), ..., (xn, yn)]*)
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fun [] ~~ [] = []
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  | (x :: xs) ~~ (y :: ys) = (x, y) :: (xs ~~ ys)
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  | _ ~~ _ = raise LIST "~~";
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(*inverse of ~~; the old 'split':
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  [(x1, y1), ..., (xn, yn)]  ===>  ([x1, ..., xn], [y1, ..., yn])*)
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fun split_list (l: ('a * 'b) list) = (map #1 l, map #2 l);
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(* prefixes, suffixes *)
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fun [] prefix _ = true
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  | (x :: xs) prefix (y :: ys) = x = y andalso (xs prefix ys)
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  | _ prefix _ = false;
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(* [x1, ..., xi, ..., xn]  --->  ([x1, ..., x(i-1)], [xi, ..., xn])
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   where xi is the first element that does not satisfy the predicate*)
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fun take_prefix (pred : 'a -> bool)  (xs: 'a list) : 'a list * 'a list =
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  let fun take (rxs, []) = (rev rxs, [])
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        | take (rxs, x :: xs) =
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            if  pred x  then  take(x :: rxs, xs)  else  (rev rxs, x :: xs)
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  in  take([], xs)  end;
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(* [x1, ..., xi, ..., xn]  --->  ([x1, ..., xi], [x(i+1), ..., xn])
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   where xi is the last element that does not satisfy the predicate*)
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fun take_suffix _ [] = ([], [])
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  | take_suffix pred (x :: xs) =
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      (case take_suffix pred xs of
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        ([], sffx) => if pred x then ([], x :: sffx) else ([x], sffx)
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      | (prfx, sffx) => (x :: prfx, sffx));
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(** integers **)
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fun inc i = (i := ! i + 1; ! i);
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fun dec i = (i := ! i - 1; ! i);
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(* lists of integers *)
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(*make the list [from, from + 1, ..., to]*)
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fun (from upto to) =
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  if from > to then [] else from :: ((from + 1) upto to);
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(*make the list [from, from - 1, ..., to]*)
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fun (from downto to) =
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  if from < to then [] else from :: ((from - 1) downto to);
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(*predicate: downto0 (is, n) <=> is = [n, n - 1, ..., 0]*)
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fun downto0 (i :: is, n) = i = n andalso downto0 (is, n - 1)
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  | downto0 ([], n) = n = ~1;
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(* convert integers to strings *)
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(*expand the number in the given base;
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  example: radixpand (2, 8) gives [1, 0, 0, 0]*)
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fun radixpand (base, num) : int list =
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  let
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    fun radix (n, tail) =
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      if n < base then n :: tail
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      else radix (n div base, (n mod base) :: tail)
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  in radix (num, []) end;
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(*expands a number into a string of characters starting from "zerochar";
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  example: radixstring (2, "0", 8) gives "1000"*)
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fun radixstring (base, zerochar, num) =
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  let val offset = ord zerochar;
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      fun chrof n = chr (offset + n)
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  in implode (map chrof (radixpand (base, num))) end;
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   373
val string_of_int = Int.toString;
wenzelm@233
   374
paulson@3407
   375
fun string_of_indexname (a,0) = a
paulson@3407
   376
  | string_of_indexname (a,i) = a ^ "_" ^ Int.toString i;
wenzelm@233
   377
wenzelm@233
   378
wenzelm@233
   379
(** strings **)
wenzelm@233
   380
wenzelm@233
   381
fun is_letter ch =
wenzelm@233
   382
  ord "A" <= ord ch andalso ord ch <= ord "Z" orelse
wenzelm@233
   383
  ord "a" <= ord ch andalso ord ch <= ord "z";
wenzelm@233
   384
wenzelm@233
   385
fun is_digit ch =
wenzelm@233
   386
  ord "0" <= ord ch andalso ord ch <= ord "9";
wenzelm@233
   387
wenzelm@233
   388
(*letter or _ or prime (')*)
wenzelm@233
   389
fun is_quasi_letter "_" = true
wenzelm@233
   390
  | is_quasi_letter "'" = true
wenzelm@233
   391
  | is_quasi_letter ch = is_letter ch;
wenzelm@233
   392
lcp@512
   393
(*white space: blanks, tabs, newlines, formfeeds*)
wenzelm@233
   394
val is_blank : string -> bool =
wenzelm@3393
   395
  fn " " => true | "\t" => true | "\n" => true | "\^L" => true | "\160" => true
wenzelm@3063
   396
    | _ => false;
wenzelm@233
   397
wenzelm@233
   398
val is_letdig = is_quasi_letter orf is_digit;
wenzelm@233
   399
wenzelm@2196
   400
(*printable chars*)
wenzelm@2196
   401
fun is_printable c = ord c > ord " " andalso ord c <= ord "~";
wenzelm@2196
   402
wenzelm@233
   403
wenzelm@233
   404
(*lower all chars of string*)
wenzelm@233
   405
val to_lower =
wenzelm@233
   406
  let
wenzelm@233
   407
    fun lower ch =
wenzelm@233
   408
      if ch >= "A" andalso ch <= "Z" then
wenzelm@233
   409
        chr (ord ch - ord "A" + ord "a")
wenzelm@233
   410
      else ch;
wenzelm@233
   411
  in implode o (map lower) o explode end;
wenzelm@233
   412
wenzelm@233
   413
lcp@512
   414
(*enclose in brackets*)
lcp@512
   415
fun enclose lpar rpar str = lpar ^ str ^ rpar;
wenzelm@255
   416
wenzelm@233
   417
(*simple quoting (does not escape special chars)*)
lcp@512
   418
val quote = enclose "\"" "\"";
wenzelm@233
   419
wenzelm@233
   420
(*space_implode "..." (explode "hello"); gives "h...e...l...l...o"*)
wenzelm@233
   421
fun space_implode a bs = implode (separate a bs);
wenzelm@233
   422
wenzelm@255
   423
val commas = space_implode ", ";
wenzelm@380
   424
val commas_quote = commas o map quote;
wenzelm@255
   425
wenzelm@233
   426
(*concatenate messages, one per line, into a string*)
wenzelm@255
   427
val cat_lines = space_implode "\n";
wenzelm@233
   428
clasohm@1290
   429
(*space_explode "." "h.e..l.lo"; gives ["h", "e", "l", "lo"]*)
clasohm@1290
   430
fun space_explode sep s =
clasohm@1290
   431
  let fun divide [] "" = []
clasohm@1290
   432
        | divide [] part = [part]
clasohm@1290
   433
        | divide (c::s) part =
clasohm@1290
   434
            if c = sep then
clasohm@1290
   435
              (if part = "" then divide s "" else part :: divide s "")
clasohm@1290
   436
            else divide s (part ^ c)
clasohm@1290
   437
  in divide (explode s) "" end;
wenzelm@233
   438
wenzelm@233
   439
wenzelm@233
   440
(** lists as sets **)
wenzelm@233
   441
wenzelm@233
   442
(*membership in a list*)
wenzelm@233
   443
fun x mem [] = false
wenzelm@233
   444
  | x mem (y :: ys) = x = y orelse x mem ys;
clasohm@0
   445
paulson@2175
   446
(*membership in a list, optimized version for ints*)
berghofe@1576
   447
fun (x:int) mem_int [] = false
berghofe@1576
   448
  | x mem_int (y :: ys) = x = y orelse x mem_int ys;
berghofe@1576
   449
paulson@2175
   450
(*membership in a list, optimized version for strings*)
berghofe@1576
   451
fun (x:string) mem_string [] = false
berghofe@1576
   452
  | x mem_string (y :: ys) = x = y orelse x mem_string ys;
berghofe@1576
   453
clasohm@0
   454
(*generalized membership test*)
wenzelm@233
   455
fun gen_mem eq (x, []) = false
wenzelm@233
   456
  | gen_mem eq (x, y :: ys) = eq (x, y) orelse gen_mem eq (x, ys);
wenzelm@233
   457
wenzelm@233
   458
wenzelm@233
   459
(*insertion into list if not already there*)
paulson@2175
   460
fun (x ins xs) = if x mem xs then xs else x :: xs;
clasohm@0
   461
paulson@2175
   462
(*insertion into list, optimized version for ints*)
paulson@2175
   463
fun (x ins_int xs) = if x mem_int xs then xs else x :: xs;
berghofe@1576
   464
paulson@2175
   465
(*insertion into list, optimized version for strings*)
paulson@2175
   466
fun (x ins_string xs) = if x mem_string xs then xs else x :: xs;
berghofe@1576
   467
clasohm@0
   468
(*generalized insertion*)
wenzelm@233
   469
fun gen_ins eq (x, xs) = if gen_mem eq (x, xs) then xs else x :: xs;
wenzelm@233
   470
wenzelm@233
   471
wenzelm@233
   472
(*union of sets represented as lists: no repetitions*)
wenzelm@233
   473
fun xs union [] = xs
wenzelm@233
   474
  | [] union ys = ys
wenzelm@233
   475
  | (x :: xs) union ys = xs union (x ins ys);
clasohm@0
   476
paulson@2175
   477
(*union of sets, optimized version for ints*)
berghofe@1576
   478
fun (xs:int list) union_int [] = xs
berghofe@1576
   479
  | [] union_int ys = ys
berghofe@1576
   480
  | (x :: xs) union_int ys = xs union_int (x ins_int ys);
berghofe@1576
   481
paulson@2175
   482
(*union of sets, optimized version for strings*)
berghofe@1576
   483
fun (xs:string list) union_string [] = xs
berghofe@1576
   484
  | [] union_string ys = ys
berghofe@1576
   485
  | (x :: xs) union_string ys = xs union_string (x ins_string ys);
berghofe@1576
   486
clasohm@0
   487
(*generalized union*)
wenzelm@233
   488
fun gen_union eq (xs, []) = xs
wenzelm@233
   489
  | gen_union eq ([], ys) = ys
wenzelm@233
   490
  | gen_union eq (x :: xs, ys) = gen_union eq (xs, gen_ins eq (x, ys));
wenzelm@233
   491
wenzelm@233
   492
wenzelm@233
   493
(*intersection*)
wenzelm@233
   494
fun [] inter ys = []
wenzelm@233
   495
  | (x :: xs) inter ys =
wenzelm@233
   496
      if x mem ys then x :: (xs inter ys) else xs inter ys;
wenzelm@233
   497
paulson@2175
   498
(*intersection, optimized version for ints*)
berghofe@1576
   499
fun ([]:int list) inter_int ys = []
berghofe@1576
   500
  | (x :: xs) inter_int ys =
berghofe@1576
   501
      if x mem_int ys then x :: (xs inter_int ys) else xs inter_int ys;
berghofe@1576
   502
paulson@2175
   503
(*intersection, optimized version for strings *)
berghofe@1576
   504
fun ([]:string list) inter_string ys = []
berghofe@1576
   505
  | (x :: xs) inter_string ys =
berghofe@1576
   506
      if x mem_string ys then x :: (xs inter_string ys) else xs inter_string ys;
berghofe@1576
   507
wenzelm@233
   508
wenzelm@233
   509
(*subset*)
wenzelm@233
   510
fun [] subset ys = true
wenzelm@233
   511
  | (x :: xs) subset ys = x mem ys andalso xs subset ys;
wenzelm@233
   512
paulson@2175
   513
(*subset, optimized version for ints*)
berghofe@1576
   514
fun ([]:int list) subset_int ys = true
berghofe@1576
   515
  | (x :: xs) subset_int ys = x mem_int ys andalso xs subset_int ys;
berghofe@1576
   516
paulson@2175
   517
(*subset, optimized version for strings*)
berghofe@1576
   518
fun ([]:string list) subset_string ys = true
berghofe@1576
   519
  | (x :: xs) subset_string ys = x mem_string ys andalso xs subset_string ys;
berghofe@1576
   520
paulson@2182
   521
(*set equality for strings*)
berghofe@1576
   522
fun eq_set_string ((xs:string list), ys) =
berghofe@1576
   523
  xs = ys orelse (xs subset_string ys andalso ys subset_string xs);
berghofe@1576
   524
paulson@2182
   525
fun gen_subset eq (xs, ys) = forall (fn x => gen_mem eq (x, ys)) xs;
paulson@2182
   526
wenzelm@265
   527
wenzelm@233
   528
(*removing an element from a list WITHOUT duplicates*)
wenzelm@233
   529
fun (y :: ys) \ x = if x = y then ys else y :: (ys \ x)
wenzelm@233
   530
  | [] \ x = [];
wenzelm@233
   531
paulson@2243
   532
fun ys \\ xs = foldl (op \) (ys,xs);
clasohm@0
   533
wenzelm@233
   534
(*removing an element from a list -- possibly WITH duplicates*)
wenzelm@233
   535
fun gen_rem eq (xs, y) = filter_out (fn x => eq (x, y)) xs;
wenzelm@233
   536
paulson@2243
   537
fun gen_rems eq = foldl (gen_rem eq);
wenzelm@233
   538
wenzelm@233
   539
wenzelm@233
   540
(*makes a list of the distinct members of the input; preserves order, takes
wenzelm@233
   541
  first of equal elements*)
wenzelm@233
   542
fun gen_distinct eq lst =
wenzelm@233
   543
  let
wenzelm@233
   544
    val memb = gen_mem eq;
clasohm@0
   545
wenzelm@233
   546
    fun dist (rev_seen, []) = rev rev_seen
wenzelm@233
   547
      | dist (rev_seen, x :: xs) =
wenzelm@233
   548
          if memb (x, rev_seen) then dist (rev_seen, xs)
wenzelm@233
   549
          else dist (x :: rev_seen, xs);
wenzelm@233
   550
  in
wenzelm@233
   551
    dist ([], lst)
wenzelm@233
   552
  end;
wenzelm@233
   553
paulson@2243
   554
fun distinct l = gen_distinct (op =) l;
wenzelm@233
   555
wenzelm@233
   556
wenzelm@233
   557
(*returns the tail beginning with the first repeated element, or []*)
wenzelm@233
   558
fun findrep [] = []
wenzelm@233
   559
  | findrep (x :: xs) = if x mem xs then x :: xs else findrep xs;
wenzelm@233
   560
wenzelm@233
   561
wenzelm@255
   562
(*returns a list containing all repeated elements exactly once; preserves
wenzelm@255
   563
  order, takes first of equal elements*)
wenzelm@255
   564
fun gen_duplicates eq lst =
wenzelm@255
   565
  let
wenzelm@255
   566
    val memb = gen_mem eq;
wenzelm@255
   567
wenzelm@255
   568
    fun dups (rev_dups, []) = rev rev_dups
wenzelm@255
   569
      | dups (rev_dups, x :: xs) =
wenzelm@255
   570
          if memb (x, rev_dups) orelse not (memb (x, xs)) then
wenzelm@255
   571
            dups (rev_dups, xs)
wenzelm@255
   572
          else dups (x :: rev_dups, xs);
wenzelm@255
   573
  in
wenzelm@255
   574
    dups ([], lst)
wenzelm@255
   575
  end;
wenzelm@255
   576
paulson@2243
   577
fun duplicates l = gen_duplicates (op =) l;
wenzelm@255
   578
wenzelm@255
   579
wenzelm@233
   580
wenzelm@233
   581
(** association lists **)
clasohm@0
   582
wenzelm@233
   583
(*association list lookup*)
wenzelm@233
   584
fun assoc ([], key) = None
wenzelm@233
   585
  | assoc ((keyi, xi) :: pairs, key) =
wenzelm@233
   586
      if key = keyi then Some xi else assoc (pairs, key);
wenzelm@233
   587
paulson@2175
   588
(*association list lookup, optimized version for ints*)
berghofe@1576
   589
fun assoc_int ([], (key:int)) = None
berghofe@1576
   590
  | assoc_int ((keyi, xi) :: pairs, key) =
berghofe@1576
   591
      if key = keyi then Some xi else assoc_int (pairs, key);
berghofe@1576
   592
paulson@2175
   593
(*association list lookup, optimized version for strings*)
berghofe@1576
   594
fun assoc_string ([], (key:string)) = None
berghofe@1576
   595
  | assoc_string ((keyi, xi) :: pairs, key) =
berghofe@1576
   596
      if key = keyi then Some xi else assoc_string (pairs, key);
berghofe@1576
   597
paulson@2175
   598
(*association list lookup, optimized version for string*ints*)
berghofe@1576
   599
fun assoc_string_int ([], (key:string*int)) = None
berghofe@1576
   600
  | assoc_string_int ((keyi, xi) :: pairs, key) =
berghofe@1576
   601
      if key = keyi then Some xi else assoc_string_int (pairs, key);
berghofe@1576
   602
wenzelm@233
   603
fun assocs ps x =
wenzelm@233
   604
  (case assoc (ps, x) of
wenzelm@233
   605
    None => []
wenzelm@233
   606
  | Some ys => ys);
wenzelm@233
   607
wenzelm@255
   608
(*two-fold association list lookup*)
wenzelm@255
   609
fun assoc2 (aal, (key1, key2)) =
wenzelm@255
   610
  (case assoc (aal, key1) of
wenzelm@255
   611
    Some al => assoc (al, key2)
wenzelm@255
   612
  | None => None);
wenzelm@255
   613
wenzelm@233
   614
(*generalized association list lookup*)
wenzelm@233
   615
fun gen_assoc eq ([], key) = None
wenzelm@233
   616
  | gen_assoc eq ((keyi, xi) :: pairs, key) =
wenzelm@233
   617
      if eq (key, keyi) then Some xi else gen_assoc eq (pairs, key);
wenzelm@233
   618
wenzelm@233
   619
(*association list update*)
wenzelm@233
   620
fun overwrite (al, p as (key, _)) =
wenzelm@233
   621
  let fun over ((q as (keyi, _)) :: pairs) =
wenzelm@233
   622
            if keyi = key then p :: pairs else q :: (over pairs)
wenzelm@233
   623
        | over [] = [p]
wenzelm@233
   624
  in over al end;
wenzelm@233
   625
wenzelm@2522
   626
fun gen_overwrite eq (al, p as (key, _)) =
wenzelm@2522
   627
  let fun over ((q as (keyi, _)) :: pairs) =
wenzelm@2522
   628
            if eq (keyi, key) then p :: pairs else q :: (over pairs)
wenzelm@2522
   629
        | over [] = [p]
wenzelm@2522
   630
  in over al end;
wenzelm@2522
   631
wenzelm@233
   632
wenzelm@233
   633
wenzelm@233
   634
(** generic tables **)
clasohm@0
   635
wenzelm@233
   636
(*Tables are supposed to be 'efficient' encodings of lists of elements distinct
wenzelm@233
   637
  wrt. an equality "eq". The extend and merge operations below are optimized
wenzelm@233
   638
  for long-term space efficiency.*)
wenzelm@233
   639
wenzelm@233
   640
(*append (new) elements to a table*)
wenzelm@233
   641
fun generic_extend _ _ _ tab [] = tab
wenzelm@233
   642
  | generic_extend eq dest_tab mk_tab tab1 lst2 =
wenzelm@233
   643
      let
wenzelm@233
   644
        val lst1 = dest_tab tab1;
wenzelm@233
   645
        val new_lst2 = gen_rems eq (lst2, lst1);
wenzelm@233
   646
      in
wenzelm@233
   647
        if null new_lst2 then tab1
wenzelm@233
   648
        else mk_tab (lst1 @ new_lst2)
wenzelm@233
   649
      end;
clasohm@0
   650
wenzelm@233
   651
(*append (new) elements of 2nd table to 1st table*)
wenzelm@233
   652
fun generic_merge eq dest_tab mk_tab tab1 tab2 =
wenzelm@233
   653
  let
wenzelm@233
   654
    val lst1 = dest_tab tab1;
wenzelm@233
   655
    val lst2 = dest_tab tab2;
wenzelm@233
   656
    val new_lst2 = gen_rems eq (lst2, lst1);
wenzelm@233
   657
  in
wenzelm@233
   658
    if null new_lst2 then tab1
wenzelm@233
   659
    else if gen_subset eq (lst1, lst2) then tab2
wenzelm@233
   660
    else mk_tab (lst1 @ new_lst2)
wenzelm@233
   661
  end;
clasohm@0
   662
wenzelm@233
   663
wenzelm@233
   664
(*lists as tables*)
paulson@2243
   665
fun extend_list tab = generic_extend (op =) I I tab;
paulson@2243
   666
fun merge_lists tab = generic_merge (op =) I I tab;
wenzelm@233
   667
wenzelm@380
   668
fun merge_rev_lists xs [] = xs
wenzelm@380
   669
  | merge_rev_lists [] ys = ys
wenzelm@380
   670
  | merge_rev_lists xs (y :: ys) =
wenzelm@380
   671
      (if y mem xs then I else cons y) (merge_rev_lists xs ys);
wenzelm@380
   672
clasohm@0
   673
clasohm@0
   674
wenzelm@233
   675
(** balanced trees **)
wenzelm@233
   676
wenzelm@233
   677
exception Balance;      (*indicates non-positive argument to balancing fun*)
wenzelm@233
   678
wenzelm@233
   679
(*balanced folding; avoids deep nesting*)
wenzelm@233
   680
fun fold_bal f [x] = x
wenzelm@233
   681
  | fold_bal f [] = raise Balance
wenzelm@233
   682
  | fold_bal f xs =
wenzelm@233
   683
      let val k = length xs div 2
wenzelm@233
   684
      in  f (fold_bal f (take(k, xs)),
wenzelm@233
   685
             fold_bal f (drop(k, xs)))
wenzelm@233
   686
      end;
wenzelm@233
   687
wenzelm@233
   688
(*construct something of the form f(...g(...(x)...)) for balanced access*)
wenzelm@233
   689
fun access_bal (f, g, x) n i =
wenzelm@233
   690
  let fun acc n i =     (*1<=i<=n*)
wenzelm@233
   691
          if n=1 then x else
wenzelm@233
   692
          let val n2 = n div 2
wenzelm@233
   693
          in  if i<=n2 then f (acc n2 i)
wenzelm@233
   694
                       else g (acc (n-n2) (i-n2))
wenzelm@233
   695
          end
wenzelm@233
   696
  in  if 1<=i andalso i<=n then acc n i else raise Balance  end;
wenzelm@233
   697
wenzelm@233
   698
(*construct ALL such accesses; could try harder to share recursive calls!*)
wenzelm@233
   699
fun accesses_bal (f, g, x) n =
wenzelm@233
   700
  let fun acc n =
wenzelm@233
   701
          if n=1 then [x] else
wenzelm@233
   702
          let val n2 = n div 2
wenzelm@233
   703
              val acc2 = acc n2
wenzelm@233
   704
          in  if n-n2=n2 then map f acc2 @ map g acc2
wenzelm@233
   705
                         else map f acc2 @ map g (acc (n-n2)) end
wenzelm@233
   706
  in  if 1<=n then acc n else raise Balance  end;
wenzelm@233
   707
wenzelm@233
   708
wenzelm@233
   709
wenzelm@2506
   710
(** orders **)
wenzelm@2506
   711
wenzelm@2506
   712
datatype order = LESS | EQUAL | GREATER;
wenzelm@2506
   713
wenzelm@2506
   714
fun intord (i, j: int) =
wenzelm@2506
   715
  if i < j then LESS
wenzelm@2506
   716
  else if i = j then EQUAL
wenzelm@2506
   717
  else GREATER;
wenzelm@2506
   718
wenzelm@2506
   719
fun stringord (a, b: string) =
wenzelm@2506
   720
  if a < b then LESS
wenzelm@2506
   721
  else if a = b then EQUAL
wenzelm@2506
   722
  else GREATER;
wenzelm@2506
   723
wenzelm@2506
   724
wenzelm@2506
   725
wenzelm@3525
   726
(** input / output and diagnostics **)
wenzelm@233
   727
paulson@2243
   728
val cd = OS.FileSys.chDir;
wenzelm@2317
   729
val pwd = OS.FileSys.getDir;
paulson@2243
   730
wenzelm@3525
   731
wenzelm@3525
   732
local
wenzelm@3525
   733
  fun out s =
wenzelm@3525
   734
    (TextIO.output (TextIO.stdOut, s); TextIO.flushOut TextIO.stdOut);
wenzelm@3525
   735
wenzelm@3525
   736
  fun lines cs =
wenzelm@3525
   737
    (case take_prefix (not_equal "\n") cs of
wenzelm@3525
   738
      (cs', []) => [implode cs']
wenzelm@3525
   739
    | (cs', _ :: cs'') => implode cs' :: lines cs'');
wenzelm@3525
   740
wenzelm@3525
   741
  fun prefix_lines prfx txt =
wenzelm@3525
   742
    txt |> explode |> lines |> map (fn s => prfx ^ s ^ "\n") |> implode;
wenzelm@3525
   743
in
wenzelm@3525
   744
wenzelm@3525
   745
(*hooks for output channels: normal, warning, error*)
wenzelm@3525
   746
val prs_fn = ref (fn s => out s);
wenzelm@3525
   747
val warning_fn = ref (fn s => out (prefix_lines "### " s));
wenzelm@3525
   748
val error_fn = ref (fn s => out (prefix_lines "*** " s));
wenzelm@3525
   749
wenzelm@3525
   750
end;
berghofe@1580
   751
berghofe@1580
   752
fun prs s = !prs_fn s;
wenzelm@233
   753
fun writeln s = prs (s ^ "\n");
wenzelm@233
   754
wenzelm@3525
   755
fun warning s = !warning_fn s;
wenzelm@233
   756
wenzelm@233
   757
(*print error message and abort to top level*)
wenzelm@233
   758
exception ERROR;
wenzelm@3553
   759
fun error_msg s = !error_fn s;
wenzelm@3553
   760
fun error s = (error_msg s; raise ERROR);
wenzelm@3553
   761
fun sys_error msg = (error_msg " !! SYSTEM ERROR !!\n"; error msg);
wenzelm@233
   762
wenzelm@233
   763
fun assert p msg = if p then () else error msg;
wenzelm@233
   764
fun deny p msg = if p then error msg else ();
wenzelm@233
   765
lcp@544
   766
(*Assert pred for every member of l, generating a message if pred fails*)
lcp@544
   767
fun assert_all pred l msg_fn = 
lcp@544
   768
  let fun asl [] = ()
paulson@2243
   769
        | asl (x::xs) = if pred x then asl xs
paulson@2243
   770
                        else error (msg_fn x)
lcp@544
   771
  in  asl l  end;
wenzelm@233
   772
wenzelm@233
   773
(*for the "test" target in Makefiles -- signifies successful termination*)
wenzelm@233
   774
fun maketest msg =
paulson@1592
   775
  (writeln msg; 
paulson@2243
   776
   let val os = TextIO.openOut "test" 
paulson@2243
   777
   in  TextIO.output (os, "Test examples ran successfully\n");
paulson@2243
   778
       TextIO.closeOut os
paulson@1592
   779
   end);
wenzelm@233
   780
wenzelm@233
   781
wenzelm@233
   782
(*print a list surrounded by the brackets lpar and rpar, with comma separator
wenzelm@233
   783
  print nothing for empty list*)
wenzelm@233
   784
fun print_list (lpar, rpar, pre: 'a -> unit) (l : 'a list) =
wenzelm@233
   785
  let fun prec x = (prs ","; pre x)
wenzelm@233
   786
  in
wenzelm@233
   787
    (case l of
wenzelm@233
   788
      [] => ()
wenzelm@233
   789
    | x::l => (prs lpar; pre x; seq prec l; prs rpar))
wenzelm@233
   790
  end;
wenzelm@233
   791
wenzelm@233
   792
(*print a list of items separated by newlines*)
wenzelm@233
   793
fun print_list_ln (pre: 'a -> unit) : 'a list -> unit =
wenzelm@233
   794
  seq (fn x => (pre x; writeln ""));
wenzelm@233
   795
wenzelm@233
   796
wenzelm@233
   797
val print_int = prs o string_of_int;
wenzelm@233
   798
wenzelm@233
   799
wenzelm@3525
   800
(* output to LaTeX / xdvi *)
wenzelm@3525
   801
fun latex s =
wenzelm@3525
   802
  execute ("( cd /tmp ; echo \"" ^ s ^
wenzelm@3525
   803
    "\" | isa2latex -s > $$.tex ; latex $$.tex ; xdvi $$.dvi ; rm $$.* ) > /dev/null &");
wenzelm@3525
   804
wenzelm@233
   805
wenzelm@233
   806
(** timing **)
wenzelm@233
   807
wenzelm@233
   808
(*unconditional timing function*)
paulson@2243
   809
fun timeit x = cond_timeit true x;
wenzelm@233
   810
wenzelm@233
   811
(*timed application function*)
wenzelm@233
   812
fun timeap f x = timeit (fn () => f x);
wenzelm@233
   813
wenzelm@233
   814
(*timed "use" function, printing filenames*)
wenzelm@233
   815
fun time_use fname = timeit (fn () =>
wenzelm@233
   816
  (writeln ("\n**** Starting " ^ fname ^ " ****"); use fname;
wenzelm@233
   817
   writeln ("\n**** Finished " ^ fname ^ " ****")));
wenzelm@233
   818
lcp@955
   819
(*For Makefiles: use the file, but exit with error code if errors found.*)
lcp@955
   820
fun exit_use fname = use fname handle _ => exit 1;
wenzelm@233
   821
wenzelm@233
   822
clasohm@1407
   823
(** filenames and paths **)
wenzelm@233
   824
clasohm@1290
   825
(*Convert UNIX filename of the form "path/file" to "path/" and "file";
wenzelm@233
   826
  if filename contains no slash, then it returns "" and "file"*)
wenzelm@233
   827
val split_filename =
wenzelm@233
   828
  (pairself implode) o take_suffix (not_equal "/") o explode;
wenzelm@233
   829
wenzelm@233
   830
val base_name = #2 o split_filename;
wenzelm@233
   831
clasohm@1290
   832
(*Merge splitted filename (path and file);
wenzelm@233
   833
  if path does not end with one a slash is appended*)
wenzelm@233
   834
fun tack_on "" name = name
wenzelm@233
   835
  | tack_on path name =
wenzelm@233
   836
      if last_elem (explode path) = "/" then path ^ name
wenzelm@233
   837
      else path ^ "/" ^ name;
wenzelm@233
   838
clasohm@1290
   839
(*Remove the extension of a filename, i.e. the part after the last '.'*)
wenzelm@233
   840
val remove_ext = implode o #1 o take_suffix (not_equal ".") o explode;
wenzelm@233
   841
clasohm@1290
   842
(*Make relative path to reach an absolute location from a different one*)
clasohm@1290
   843
fun relative_path cur_path dest_path =
clasohm@1290
   844
  let (*Remove common beginning of both paths and make relative path*)
clasohm@1290
   845
      fun mk_relative [] [] = []
clasohm@1290
   846
        | mk_relative [] ds = ds
clasohm@1290
   847
        | mk_relative cs [] = map (fn _ => "..") cs
clasohm@1290
   848
        | mk_relative (c::cs) (d::ds) =
clasohm@1290
   849
            if c = d then mk_relative cs ds
clasohm@1290
   850
            else ".." :: map (fn _ => "..") cs @ (d::ds);
clasohm@1290
   851
  in if cur_path = "" orelse hd (explode cur_path) <> "/" orelse
clasohm@1290
   852
        dest_path = "" orelse hd (explode dest_path) <> "/" then
clasohm@1290
   853
       error "Relative or empty path passed to relative_path"
clasohm@1290
   854
     else ();
clasohm@1290
   855
     space_implode "/" (mk_relative (space_explode "/" cur_path)
clasohm@1290
   856
                                    (space_explode "/" dest_path))
clasohm@1290
   857
  end;
wenzelm@233
   858
clasohm@1407
   859
(*Determine if absolute path1 is a subdirectory of absolute path2*)
clasohm@1407
   860
fun path1 subdir_of path2 =
clasohm@1407
   861
  if hd (explode path1) <> "/" orelse hd (explode path2) <> "/" then
clasohm@1407
   862
    error "Relative or empty path passed to subdir_of"
clasohm@1407
   863
  else (space_explode "/" path2) prefix (space_explode "/" path1);
clasohm@1407
   864
clasohm@1456
   865
fun absolute_path cwd file =
clasohm@1456
   866
  let fun rm_points [] result = rev result
clasohm@1456
   867
        | rm_points (".."::ds) result = rm_points ds (tl result)
clasohm@1456
   868
        | rm_points ("."::ds) result = rm_points ds result
clasohm@1456
   869
        | rm_points (d::ds) result = rm_points ds (d::result);
clasohm@1456
   870
  in if file = "" then ""
clasohm@1456
   871
     else if hd (explode file) = "/" then file
clasohm@1456
   872
     else "/" ^ space_implode "/"
clasohm@1456
   873
                  (rm_points (space_explode "/" (tack_on cwd file)) [])
clasohm@1456
   874
  end;
clasohm@1456
   875
wenzelm@233
   876
wenzelm@233
   877
(** misc functions **)
wenzelm@233
   878
wenzelm@233
   879
(*use the keyfun to make a list of (x, key) pairs*)
clasohm@0
   880
fun make_keylist (keyfun: 'a->'b) : 'a list -> ('a * 'b) list =
wenzelm@233
   881
  let fun keypair x = (x, keyfun x)
wenzelm@233
   882
  in map keypair end;
clasohm@0
   883
wenzelm@233
   884
(*given a list of (x, key) pairs and a searchkey
clasohm@0
   885
  return the list of xs from each pair whose key equals searchkey*)
clasohm@0
   886
fun keyfilter [] searchkey = []
wenzelm@233
   887
  | keyfilter ((x, key) :: pairs) searchkey =
wenzelm@233
   888
      if key = searchkey then x :: keyfilter pairs searchkey
wenzelm@233
   889
      else keyfilter pairs searchkey;
clasohm@0
   890
clasohm@0
   891
clasohm@0
   892
(*Partition list into elements that satisfy predicate and those that don't.
wenzelm@233
   893
  Preserves order of elements in both lists.*)
clasohm@0
   894
fun partition (pred: 'a->bool) (ys: 'a list) : ('a list * 'a list) =
clasohm@0
   895
    let fun part ([], answer) = answer
wenzelm@233
   896
          | part (x::xs, (ys, ns)) = if pred(x)
wenzelm@233
   897
            then  part (xs, (x::ys, ns))
wenzelm@233
   898
            else  part (xs, (ys, x::ns))
wenzelm@233
   899
    in  part (rev ys, ([], []))  end;
clasohm@0
   900
clasohm@0
   901
clasohm@0
   902
fun partition_eq (eq:'a * 'a -> bool) =
clasohm@0
   903
    let fun part [] = []
wenzelm@233
   904
          | part (x::ys) = let val (xs, xs') = partition (apl(x, eq)) ys
wenzelm@233
   905
                           in (x::xs)::(part xs') end
clasohm@0
   906
    in part end;
clasohm@0
   907
clasohm@0
   908
wenzelm@233
   909
(*Partition a list into buckets  [ bi, b(i+1), ..., bj ]
clasohm@0
   910
   putting x in bk if p(k)(x) holds.  Preserve order of elements if possible.*)
clasohm@0
   911
fun partition_list p i j =
wenzelm@233
   912
  let fun part k xs =
wenzelm@233
   913
            if k>j then
clasohm@0
   914
              (case xs of [] => []
clasohm@0
   915
                         | _ => raise LIST "partition_list")
clasohm@0
   916
            else
wenzelm@233
   917
            let val (ns, rest) = partition (p k) xs;
wenzelm@233
   918
            in  ns :: part(k+1)rest  end
clasohm@0
   919
  in  part i end;
clasohm@0
   920
clasohm@0
   921
wenzelm@233
   922
(* sorting *)
wenzelm@233
   923
wenzelm@233
   924
(*insertion sort; stable (does not reorder equal elements)
wenzelm@233
   925
  'less' is less-than test on type 'a*)
wenzelm@233
   926
fun sort (less: 'a*'a -> bool) =
clasohm@0
   927
  let fun insert (x, []) = [x]
wenzelm@233
   928
        | insert (x, y::ys) =
wenzelm@233
   929
              if less(y, x) then y :: insert (x, ys) else x::y::ys;
clasohm@0
   930
      fun sort1 [] = []
clasohm@0
   931
        | sort1 (x::xs) = insert (x, sort1 xs)
clasohm@0
   932
  in  sort1  end;
clasohm@0
   933
wenzelm@41
   934
(*sort strings*)
wenzelm@41
   935
val sort_strings = sort (op <= : string * string -> bool);
wenzelm@41
   936
wenzelm@41
   937
wenzelm@233
   938
(* transitive closure (not Warshall's algorithm) *)
clasohm@0
   939
wenzelm@233
   940
fun transitive_closure [] = []
wenzelm@233
   941
  | transitive_closure ((x, ys)::ps) =
wenzelm@233
   942
      let val qs = transitive_closure ps
paulson@2182
   943
          val zs = foldl (fn (zs, y) => assocs qs y union_string zs) (ys, ys)
paulson@2182
   944
          fun step(u, us) = (u, if x mem_string us then zs union_string us 
paulson@2243
   945
                                else us)
wenzelm@233
   946
      in (x, zs) :: map step qs end;
clasohm@0
   947
clasohm@0
   948
wenzelm@233
   949
(* generating identifiers *)
clasohm@0
   950
clasohm@0
   951
local
wenzelm@233
   952
  val a = ord "a" and z = ord "z" and A = ord "A" and Z = ord "Z"
wenzelm@233
   953
  and k0 = ord "0" and k9 = ord "9"
paulson@2003
   954
paulson@2806
   955
  val seedr = ref 0;
clasohm@0
   956
in
clasohm@0
   957
paulson@2003
   958
(*Maps 0-63 to A-Z, a-z, 0-9 or _ or ' for generating random identifiers*)
paulson@2003
   959
fun newid n = 
paulson@2003
   960
  let fun char i =
paulson@2003
   961
               if i<26 then chr (A+i)
paulson@2003
   962
          else if i<52 then chr (a+i-26)
paulson@2003
   963
          else if i<62 then chr (k0+i-52)
paulson@2003
   964
          else if i=62 then "_"
paulson@2003
   965
          else  (*i=63*)    "'"
paulson@2003
   966
  in  implode (map char (radixpand (64,n)))  end;
paulson@2003
   967
paulson@2806
   968
(*Freshly generated identifiers with given prefix; MUST start with a letter*)
paulson@2003
   969
fun gensym pre = pre ^ 
paulson@2806
   970
                 (#1(newid (!seedr), 
paulson@2806
   971
                     seedr := 1+ !seedr))
paulson@2003
   972
clasohm@0
   973
(*Increment a list of letters like a reversed base 26 number.
wenzelm@233
   974
  If head is "z", bumps chars in tail.
clasohm@0
   975
  Digits are incremented as if they were integers.
clasohm@0
   976
  "_" and "'" are not changed.
wenzelm@233
   977
  For making variants of identifiers.*)
clasohm@0
   978
clasohm@0
   979
fun bump_int_list(c::cs) = if c="9" then "0" :: bump_int_list cs else
wenzelm@233
   980
        if k0 <= ord(c) andalso ord(c) < k9 then chr(ord(c)+1) :: cs
wenzelm@233
   981
        else "1" :: c :: cs
clasohm@0
   982
  | bump_int_list([]) = error("bump_int_list: not an identifier");
clasohm@0
   983
wenzelm@233
   984
fun bump_list([], d) = [d]
wenzelm@233
   985
  | bump_list(["'"], d) = [d, "'"]
wenzelm@233
   986
  | bump_list("z"::cs, _) = "a" :: bump_list(cs, "a")
wenzelm@233
   987
  | bump_list("Z"::cs, _) = "A" :: bump_list(cs, "A")
wenzelm@233
   988
  | bump_list("9"::cs, _) = "0" :: bump_int_list cs
wenzelm@233
   989
  | bump_list(c::cs, _) = let val k = ord(c)
wenzelm@233
   990
        in if (a <= k andalso k < z) orelse (A <= k andalso k < Z) orelse
wenzelm@233
   991
              (k0 <= k andalso k < k9) then chr(k+1) :: cs else
wenzelm@233
   992
           if c="'" orelse c="_" then c :: bump_list(cs, "") else
wenzelm@233
   993
                error("bump_list: not legal in identifier: " ^
wenzelm@233
   994
                        implode(rev(c::cs)))
wenzelm@233
   995
        end;
clasohm@0
   996
clasohm@0
   997
end;
clasohm@0
   998
wenzelm@233
   999
fun bump_string s : string = implode (rev (bump_list(rev(explode s), "")));
wenzelm@41
  1000
wenzelm@41
  1001
wenzelm@233
  1002
(* lexical scanning *)
clasohm@0
  1003
wenzelm@233
  1004
(*scan a list of characters into "words" composed of "letters" (recognized by
wenzelm@233
  1005
  is_let) and separated by any number of non-"letters"*)
wenzelm@233
  1006
fun scanwords is_let cs =
clasohm@0
  1007
  let fun scan1 [] = []
wenzelm@233
  1008
        | scan1 cs =
wenzelm@233
  1009
            let val (lets, rest) = take_prefix is_let cs
wenzelm@233
  1010
            in implode lets :: scanwords is_let rest end;
wenzelm@233
  1011
  in scan1 (#2 (take_prefix (not o is_let) cs)) end;
clasohm@24
  1012
clasohm@1364
  1013
end;
clasohm@1364
  1014
paulson@1592
  1015
(*Variable-branching trees: for proof terms*)
paulson@1592
  1016
datatype 'a mtree = Join of 'a * 'a mtree list;
paulson@1592
  1017
clasohm@1364
  1018
open Library;