[fjh at cs.mu.OZ.AU: Re: [m-rev.] For review: updates to string.m]

[Ralph Becket]

Fergus Henderson, Sunday, 27 October 2002:
> Could you please take a look at this one?
> This issue is "release-critical", IMHO.

Sorry - I thought  I'd addressed this one ages ago.


Estimated hours taken: 0.5
Branches: main

library/string.m:
	Changed the behaviour of string__foldr_substring to be "safe"
	in the sense that it is equivalent to calling
	    foldr(Closure, substring(String, Start, Count), Acc0, Acc)
	rather than
	    foldr(Closure, unsafe_substring(String, Start, Count), Acc0, Acc).

Index: string.m
===================================================================
RCS file: /home/mercury1/repository/mercury/library/string.m,v
retrieving revision 1.176
diff -u -r1.176 string.m
--- string.m	8 Aug 2002 08:14:13 -0000	1.176
+++ string.m	28 Oct 2002 04:52:13 -0000
@@ -365,7 +365,7 @@
 		in, out) is multi.
 %	string__foldr_substring(Closure, String, Start, Count, Acc0, Acc)
 %	is equivalent to string__foldr(Closure, SubString, Acc0, Acc)
-%	where SubString = string__unsafe_substring(String, Start, Count).
+%	where SubString = string__substring(String, Start, Count).
 
 :- func string__words(pred(char), string) = list(string).
 :- mode string__words(pred(in) is semidet, in) = out is det.
@@ -676,11 +676,28 @@
 string__foldr(Closure, String, Acc0, Acc) :-
 	string__foldr_substring(Closure, String, 0, length(String), Acc0, Acc).
 
-string__foldr_substring(Closure, String, I, Count, Acc0, Acc) :-
+string__foldr_substring(Closure, String, Start0, Count0, Acc0, Acc) :-
+	Start = max(0, Start0),
+	Count = min(Count0, length(String) - Start),
+	string__foldr_substring_2(Closure, String, Start, Count, Acc0, Acc).
+
+:- pred string__foldr_substring_2(pred(char, T, T), string, int, int, T, T).
+:- mode string__foldr_substring_2(pred(in, in, out) is det, in, in, in,
+		in, out) is det.
+:- mode string__foldr_substring_2(pred(in, di, uo) is det, in, in, in,
+		di, uo) is det.
+:- mode string__foldr_substring_2(pred(in, in, out) is semidet, in, in, in,
+		in, out) is semidet.
+:- mode string__foldr_substring_2(pred(in, in, out) is nondet, in, in, in,
+		in, out) is nondet.
+:- mode string__foldr_substring_2(pred(in, in, out) is multi, in, in, in,
+		in, out) is multi.
+
+string__foldr_substring_2(Closure, String, I, Count, Acc0, Acc) :-
 	( if 0 < Count then
 		Closure(string__unsafe_index(String, I + Count - 1),
 			Acc0, Acc1),
-		string__foldr_substring(Closure, String, I, Count - 1,
+		string__foldr_substring_2(Closure, String, I, Count - 1,
 			Acc1, Acc )
 	  else
 	  	Acc = Acc0

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