[m-rev.] for review: string__substring in Mercury

[Yoann Dubreuil]

Hi,


===================================================================


Estimated hours taken: 1 
User: ydu
Branches: main

library/string.m:
	Implementation of string__substring in Mercury.

Index: string.m
===================================================================
RCS file: /home/mercury1/repository/mercury/library/string.m,v
retrieving revision 1.158
diff -u -r1.158 string.m
--- string.m	6 Sep 2001 12:05:20 -0000	1.158
+++ string.m	7 Sep 2001 13:33:50 -0000
@@ -449,7 +449,7 @@
 %-----------------------------------------------------------------------------%
 
 :- implementation.
-:- import_module bool, std_util, int, float, require.
+:- import_module bool, std_util, int, float, require, integer.
 
 :- pred string__to_int_list(string, list(int)).
 :- mode string__to_int_list(out, in) is det.
@@ -2115,6 +2115,21 @@
 %	string__substring(String, Start, Count, Substring):
 */
 
+string__substring(Str::in, Start::in, Count::in, SubString::out) :- 
+	string__to_char_list(Str, Chars0),
+	string__length(Str, Length),
+	( Count >= Length - Start ->
+		Count1 = Length - Start
+	;
+		Count1 = Count
+	),
+	( list__drop(Start, Chars0, Chars1),
+	  list__take(Count1, Chars1, Chars) ->
+		SubString = string__from_char_list(Chars)
+	;
+			SubString = ""
+	).
+
 :- pragma foreign_proc("C",
 	string__substring(Str::in, Start::in, Count::in,
 		SubString::out),
@@ -2136,14 +2151,6 @@
 		SubString[Count] = '\\0';
 	}
 }").
-:- pragma foreign_proc("MC++",
-	string__substring(_Str::in, _Start::in, _Count::in,
-		_SubString::out),
-		[will_not_call_mercury, thread_safe],
-"{
-	mercury::runtime::Errors::SORRY(""c code for this function"");
-}").
-
 
 /*
 :- pred string__unsafe_substring(string, int, int, string).


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