[m-rev.] for review: tuple syntax fix

[Fergus Henderson]

I was unpleasantly surprised to find that `{(x,y)}' parses as '{}'/2
rather than as '{}'/1.  If I explicitly write the parentheses, then
the compiler should not ignore them.  Hence the following patch.

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Estimated hours taken: 1
Branches: main

library/parser.m:
	Change the parsing for tuples to be similar to the parsing
	for functor arguments, so that e.g. "{(x,y)}" parses as
	"'{}'(','(x,y))" rather than as "'{}'(x,y)", and "{ x :- y }"
	parses successfully as is, rather than needing to be rewritten as
	"{ (x :- y) }".

Workspace: /home/ceres/fjh/mercury
Index: library/parser.m
===================================================================
RCS file: /home/mercury1/repository/mercury/library/parser.m,v
retrieving revision 1.38
diff -u -d -r1.38 parser.m
--- library/parser.m	8 Nov 2001 15:30:38 -0000	1.38
+++ library/parser.m	7 Mar 2002 19:45:50 -0000
@@ -593,32 +593,41 @@
 		% it as "'{}'(1,2,3)". This makes the
 		% structure of tuple functors the same
 		% as other functors.
-		parser__parse_term(SubTerm0),
-		( { SubTerm0 = ok(SubTerm) } ->
-			{ conjunction_to_list(SubTerm, ArgTerms) },
-			( parser__get_token(close_curly) ->
-				{ Term = ok(term__functor(term__atom("{}"), 
-					ArgTerms, TermContext)) }
-			;
-				parser__unexpected("expecting `}' or operator",
-					Term)
-			)
-		;
-			% propagate error upwards
-			{ Term = SubTerm0 }
-		)
+		parser__parse_tuple_args(ArgTerms)
 	).
 
-:- pred parser__conjunction_to_list(term(T), list(term(T))).
-:- mode parser__conjunction_to_list(in, out) is det.
+:- pred parser__parse_tuple_args(parse(list(term(T))),
+	parser__state(Ops, T), parser__state(Ops, T)) <= op_table(Ops).
+:- mode parser__parse_tuple_args(out, in, out) is det.
 
-parser__conjunction_to_list(Term, ArgTerms) :-
-	( Term = term__functor(term__atom(","), [LeftTerm, RightTerm], _) ->
-		parser__conjunction_to_list(RightTerm, ArgTerms0),
-		ArgTerms = [LeftTerm | ArgTerms0]
+parser__parse_tuple_args(List) -->
+	parser__parse_arg(Arg0),
+	(   { Arg0 = ok(Arg) },
+	    ( parser__get_token(Token, Context) ->
+		( { Token = comma } ->
+		    parser__parse_tuple_args(Tail0),
+		    ( { Tail0 = ok(Tail) } ->
+			{ List = ok([Arg|Tail]) }
+		    ;
+			% propagate error upwards
+		        { List = Tail0 }
+		    )
+		; { Token = close } ->
+		    { List = ok([Arg]) }
+		;
+		    parser__unexpected_tok(Token, Context,
+				"expected `,', `}', or operator", List)
+		)
+	    ;
+		parser__error("unexpected end-of-file in tuple argument list",
+			List)
+	    )
 	;
-		ArgTerms = [Term]
+	    { Arg0 = error(Message, Tokens) },
+	    % propagate error upwards
+	    { List = error(Message, Tokens) }
 	).
+
 
 :- pred parser__check_for_higher_order_term(parse(term(T)), token_context,
 	parse(term(T)), parser__state(Ops, T),

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