bug fix for arg/3 and argument/3

[Fergus Henderson]

Estimated hours taken: 0.5

library/std_util.m:
	Fix a bug in Tyson's change from `arg' (1-based) to `argument'
	(0-based) -- he hadn't changed the pragma c_code for `argument'
	to assume the argument passed was 0-based.

Index: std_util.m
===================================================================
RCS file: /home/staff/zs/imp/mercury/library/std_util.m,v
retrieving revision 1.79
diff -u -r1.79 std_util.m
--- std_util.m	1997/04/23 06:37:33	1.79
+++ std_util.m	1997/04/24 01:49:56
@@ -2043,12 +2043,12 @@
 	restore_transient_registers();
 
 		/* Check range */
-	success = (ArgumentIndex > 0 && ArgumentIndex <= info.arity);
+	success = (ArgumentIndex >= 0 && ArgumentIndex < info.arity);
 	if (success) {
 
 			/* Allocate enough room for a univ */
 		incr_hp(Argument, 2);
-		arg_pseudo_type_info = info.type_info_vector[ArgumentIndex - 1];
+		arg_pseudo_type_info = info.type_info_vector[ArgumentIndex];
 		if (arg_pseudo_type_info < TYPELAYOUT_MAX_VARINT) {
 			field(0, Argument, UNIV_OFFSET_FOR_TYPEINFO) = 
 				((Word *) TypeInfo_for_T)[arg_pseudo_type_info];
@@ -2058,7 +2058,7 @@
 				arg_pseudo_type_info;
 		}
 		field(0, Argument, UNIV_OFFSET_FOR_DATA) = 
-			info.argument_vector[ArgumentIndex - 1];
+			info.argument_vector[ArgumentIndex];
 	}
 
 	/* Free the allocated type_info_vector, since we just copied

-- 
Fergus Henderson <fjh at cs.mu.oz.au>   |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3         |     -- the last words of T. S. Garp.