# HG changeset patch
# User wenzelm
# Date 880123659 -3600
# Node ID 8336e8d7a6807ae9de688912698ebab95f9d5036
# Parent  a770eae2cdb0f5fa1f68c75ee3a738b3f168bed2
replaced by seq.ML;

diff -r a770eae2cdb0 -r 8336e8d7a680 src/Pure/sequence.ML
--- a/src/Pure/sequence.ML	Fri Nov 21 15:41:27 1997 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,141 +0,0 @@
-(*  Title: 	sequence
-    ID:         $Id$
-    Author: 	Lawrence C Paulson, Cambridge University Computer Laboratory
-    Copyright   1988  University of Cambridge
-
-Unbounded sequences implemented by closures.
-
-RECOMPUTES if sequence is re-inspected.
-
-Memoing, using polymorphic refs, was found to be slower!  (More GCs)
-*)
-
-
-signature SEQUENCE = 
-  sig
-  type 'a seq
-  val append	: 'a seq * 'a seq -> 'a seq
-  val chop	: int * 'a seq -> 'a list * 'a seq
-  val cons	: 'a * 'a seq -> 'a seq
-  val filters	: ('a -> bool) -> 'a seq -> 'a seq
-  val flats	: 'a seq seq -> 'a seq
-  val hd	: 'a seq -> 'a
-  val interleave: 'a seq * 'a seq -> 'a seq
-  val its_right	: ('a * 'b seq -> 'b seq) -> 'a seq * 'b seq -> 'b seq
-  val list_of_s	: 'a seq -> 'a list
-  val mapp	: ('a -> 'b) -> 'a seq -> 'b seq -> 'b seq
-  val maps	: ('a -> 'b) -> 'a seq -> 'b seq
-  val null	: 'a seq
-  val prints	: (int -> 'a -> unit) -> int -> 'a seq -> unit
-  val pull	: 'a seq -> ('a * 'a seq) option
-  val s_of_list	: 'a list -> 'a seq
-  val seqof	: (unit -> ('a * 'a seq) option) -> 'a seq
-  val single	: 'a -> 'a seq
-  val tl	: 'a seq -> 'a seq
-  end;
-
-
-structure Sequence : SEQUENCE = 
-struct
-    
-datatype 'a seq = Seq of unit -> ('a * 'a seq)option;
-
-(*Return next sequence element as None or Some(x,str) *)
-fun pull(Seq f) = f();
-
-(*Head and tail.  Beware of calling the sequence function twice!!*)
-fun hd s = #1 (the (pull s))
-and tl s = #2 (the (pull s));
-
-(*the abstraction for making a sequence*)
-val seqof = Seq;
-
-(*prefix an element to the sequence
-    use cons(x,s) only if evaluation of s need not be delayed,
-      otherwise use seqof(fn()=> Some(x,s)) *)
-fun cons all = Seq(fn()=>Some all);
-
-(*the empty sequence*)
-val null = Seq(fn()=>None);
-
-fun single(x) = cons (x, null);
-
-(*The list of the first n elements, paired with rest of sequence.
-  If length of list is less than n, then sequence had less than n elements.*)
-fun chop (n:int, s: 'a seq): 'a list * 'a seq =
-  if n<=0 then ([],s)
-  else case pull(s) of
-           None => ([],s)
-         | Some(x,s') => let val (xs,s'') = chop (n-1,s')
-		         in  (x::xs, s'')  end;
-
-(*conversion from sequence to list*)
-fun list_of_s (s: 'a seq) : 'a list = case pull(s) of
-        None => []
-      | Some(x,s') => x :: list_of_s s';
-
-
-(*conversion from list to sequence*)
-fun s_of_list []     = null
-  | s_of_list (x::l) = cons (x, s_of_list l);
-
-
-(*functional to print a sequence, up to "count" elements
-  the function prelem should print the element number and also the element*)
-fun prints (prelem: int -> 'a -> unit) count (s: 'a seq) : unit =
-  let fun pr (k,s) = 
-	   if k>count then ()
-	   else case pull(s) of
-	       None => ()
-	     | Some(x,s') => (prelem k x;  prs"\n";  pr (k+1, s'))
-  in  pr(1,s)  end;
-
-(*Map the function f over the sequence, making a new sequence*)
-fun maps f xq = seqof (fn()=> case pull(xq) of
-        None       => None
-      | Some(x,yq) => Some(f x,  maps f yq));
-
-(*Sequence append:  put the elements of xq in front of those of yq*)
-fun append (xq,yq)  =
-  let fun copy xq = seqof (fn()=>
-	    case pull xq of  
-		 None       => pull yq
-	       | Some(x,xq') => Some (x, copy xq'))
-  in  copy xq end;
-
-(*Interleave elements of xq with those of yq -- fairer than append*)
-fun interleave (xq,yq) = seqof (fn()=>
-      case pull(xq) of  
-          None       => pull yq
-	| Some(x,xq') => Some (x, interleave(yq, xq')));
-
-(*map over a sequence xq, append the sequence yq*)
-fun mapp f xq yq =
-  let fun copy s = seqof (fn()=> 
-            case pull(s) of
-	        None       => pull(yq)
-              | Some(x,xq') => Some(f x, copy xq'))
-  in  copy xq end;
-
-(*Flatten a sequence of sequences to a single sequence. *)
-fun flats ss = seqof (fn()=> case pull(ss) of
-        None => None
-      | Some(s,ss') =>  pull(append(s, flats ss')));
-
-(*accumulating a function over a sequence;  this is lazy*)
-fun its_right (f: 'a * 'b seq -> 'b seq) (s: 'a seq, bstr: 'b seq) : 'b seq =
-  let fun its s = seqof (fn()=>
-            case pull(s) of
-	        None       => pull bstr
-	      | Some(a,s') => pull(f(a, its s')))
-  in  its s end; 
-
-fun filters pred xq =
-  let fun copy s = seqof (fn()=> 
-            case pull(s) of
-	        None       => None
-              | Some(x,xq') => if pred x then Some(x, copy xq')
-			       else pull (copy xq') )
-  in  copy xq end
-
-end;