author  obua 
Fri, 16 Sep 2005 21:02:15 +0200  
changeset 17440  df77edc4f5d0 
parent 16854  fdd362b7e980 
permissions  rwrr 
10769  1 
(* Title: TFL/utils.ML 
2 
ID: $Id$ 

3 
Author: Konrad Slind, Cambridge University Computer Laboratory 

4 
Copyright 1997 University of Cambridge 

5 

6 
Basic utilities. 

7 
*) 

8 

9 
signature UTILS = 

10 
sig 

11 
exception ERR of {module: string, func: string, mesg: string} 

12 
val C: ('a > 'b > 'c) > 'b > 'a > 'c 

13 
val end_itlist: ('a > 'a > 'a) > 'a list > 'a 

14 
val itlist2: ('a > 'b > 'c > 'c) > 'a list > 'b list > 'c > 'c 

15 
val pluck: ('a > bool) > 'a list > 'a * 'a list 

16 
val zip3: 'a list > 'b list > 'c list > ('a*'b*'c) list 

17 
val take: ('a > 'b) > int * 'a list > 'b list 

18 
end; 

19 

20 
structure Utils: UTILS = 

21 
struct 

22 

23 
(*standard exception for TFL*) 

24 
exception ERR of {module: string, func: string, mesg: string}; 

25 

26 
fun UTILS_ERR func mesg = ERR {module = "Utils", func = func, mesg = mesg}; 

27 

28 

29 
fun C f x y = f y x 

30 

16854
fdd362b7e980
removed itlist, rev_itlist  use fold_rev, fold instead;
wenzelm
parents:
10769
diff
changeset

31 
fun end_itlist f [] = raise (UTILS_ERR "end_itlist" "list too short") 
fdd362b7e980
removed itlist, rev_itlist  use fold_rev, fold instead;
wenzelm
parents:
10769
diff
changeset

32 
 end_itlist f [x] = x 
fdd362b7e980
removed itlist, rev_itlist  use fold_rev, fold instead;
wenzelm
parents:
10769
diff
changeset

33 
 end_itlist f (x :: xs) = f x (end_itlist f xs); 
10769  34 

35 
fun itlist2 f L1 L2 base_value = 

36 
let fun it ([],[]) = base_value 

37 
 it ((a::rst1),(b::rst2)) = f a b (it (rst1,rst2)) 

38 
 it _ = raise UTILS_ERR "itlist2" "different length lists" 

39 
in it (L1,L2) 

40 
end; 

41 

42 
fun pluck p = 

43 
let fun remv ([],_) = raise UTILS_ERR "pluck" "item not found" 

44 
 remv (h::t, A) = if p h then (h, rev A @ t) else remv (t,h::A) 

45 
in fn L => remv(L,[]) 

46 
end; 

47 

48 
fun take f = 

49 
let fun grab(0,L) = [] 

50 
 grab(n, x::rst) = f x::grab(n1,rst) 

51 
in grab 

52 
end; 

53 

54 
fun zip3 [][][] = [] 

55 
 zip3 (x::l1) (y::l2) (z::l3) = (x,y,z)::zip3 l1 l2 l3 

56 
 zip3 _ _ _ = raise UTILS_ERR "zip3" "different lengths"; 

57 

58 

59 
end; 