diff: simplify.m: improvement to stayl's change

[Fergus Henderson]

Hi Simon,

I noticed that you committed the change that I suggest to simplify.m
without including it in the log message or mailing the diff to
mercury-developers.  Tut, tut ;-)


compiler/simplify.m:
	A small improvement to stayl's previous change to
	append `fail' at the end of conjunctions that can't
	succeed (to preserve mode correctness): when checking whether a
	goal is `fail' use unification, rather than fail_goal/1.
	fail_goal/1 is intended for generating fail goals, not for
	testing for them.
	Also fix a spelling error in a comment.

cvs diff  compiler/simplify.m
Index: compiler/simplify.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/simplify.m,v
retrieving revision 1.53
diff -u -r1.53 simplify.m
--- simplify.m	1998/02/12 01:17:44	1.53
+++ simplify.m	1998/02/12 02:05:51
@@ -886,12 +886,12 @@
 		simplify__conjoin_goal_and_rev_goal_list(Goal1,
 			RevGoals0, RevGoals1),
 
-		( (fail_goal(Goal1) ; Goals0 = []) ->
+		( (Goal1 = disj([], _) - _ ; Goals0 = []) ->
 			RevGoals = RevGoals1
 		;
 			% We insert an explicit failure at the end
 			% of the non-succeeding conjunction. This
-			% is necessary, since the unreachablility of
+			% is necessary, since the unreachability of
 			% the instmap could have been derived using
 			% inferred determinism information. Without the
 			% explicit fail goal, mode errors could result if mode


-- 
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"
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