author  oheimb 
Wed, 12 Nov 1997 12:34:43 +0100  
changeset 4206  688050e83d89 
parent 3391  5e45dd3b64e9 
child 9867  bf8300fa4238 
permissions  rwrr 
3302  1 
(* Title: TFL/utils 
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ID: $Id$ 

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Author: Konrad Slind, Cambridge University Computer Laboratory 

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Copyright 1997 University of Cambridge 

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Basic utilities 
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*) 

3245
241838c01caf
Removal of redundant code (unused or already present in Isabelle.
paulson
parents:
3191
diff
changeset

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241838c01caf
Removal of redundant code (unused or already present in Isabelle.
paulson
parents:
3191
diff
changeset

9 
structure Utils = 
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struct 
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(* Standard exception for TFL. *) 

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

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

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(* Simple combinators *) 

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fun C f x y = f y x 

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fun itlist f L base_value = 

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let fun it [] = base_value 

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 it (a::rst) = f a (it rst) 

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in it L 

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end; 

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fun rev_itlist f = 

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let fun rev_it [] base = base 

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 rev_it (a::rst) base = rev_it rst (f a base) 

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in rev_it 

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end; 

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fun end_itlist f = 

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let fun endit [] = raise UTILS_ERR{func="end_itlist", mesg="list too short"} 

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 endit alist = 

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let val (base::ralist) = rev alist 

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in itlist f (rev ralist) base 

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end 

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in endit 

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end; 

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fun itlist2 f L1 L2 base_value = 

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

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

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 it _ = raise UTILS_ERR{func="itlist2",mesg="different length lists"} 

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in it (L1,L2) 

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end; 

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fun pluck p = 

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let fun remv ([],_) = raise UTILS_ERR{func="pluck",mesg = "item not found"} 

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

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

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end; 

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fun take f = 

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let fun grab(0,L) = [] 

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

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in grab 

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end; 

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fun zip3 [][][] = [] 

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

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 zip3 _ _ _ = raise UTILS_ERR{func="zip3",mesg="different lengths"}; 

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fun can f x = (f x ; true) handle _ => false; 

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fun holds P x = P x handle _ => false; 

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fun sort R = 

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let fun part (m, []) = ([],[]) 

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 part (m, h::rst) = 

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let val (l1,l2) = part (m,rst) 

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in if (R h m) then (h::l1, l2) 

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else (l1, h::l2) end 

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fun qsort [] = [] 

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 qsort (h::rst) = 

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let val (l1,l2) = part(h,rst) 

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in qsort l1@ [h] @qsort l2 

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end 

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in qsort 

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end; 

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end; (* Utils *) 