[m-rev.] diff: avoid error message for empty browser commands

[Zoltan Somogyi]

browser/browse.m:
browser/parse.m:
	Add a new browser "command", empty, to represent command lines without
	tokens. This allows us to avoid giving an error message if the user
	just hits return at a browser prompt.

	Use a better variable name.

Zoltan.

cvs diff: Diffing .
cvs diff: Diffing bindist
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cvs diff: Diffing browser
Index: browser/browse.m
===================================================================
RCS file: /home/mercury1/repository/mercury/browser/browse.m,v
retrieving revision 1.28
diff -u -b -r1.28 browse.m
--- browser/browse.m	2002/04/16 13:54:29	1.28
+++ browser/browse.m	2002/07/03 08:01:07
@@ -335,7 +335,10 @@
 	% XXX The commands `set', `ls' and `print' should allow the format
 	% to be specified by an option.  In each case we instead pass `no' to
 	% the respective handler.
-	( { Command = unknown },
+	( { Command = empty },
+		{ Quit = no },
+		{ Info = Info0 }
+	; { Command = unknown },
 		write_string_debugger(Debugger, 
 			"Error: unknown command or syntax error.\n"),
 		write_string_debugger(Debugger, "Type \"help\" for help.\n"),
Index: browser/parse.m
===================================================================
RCS file: /home/mercury1/repository/mercury/browser/parse.m,v
retrieving revision 1.13
diff -u -b -r1.13 parse.m
--- browser/parse.m	2001/12/19 06:44:47	1.13
+++ browser/parse.m	2002/07/03 08:04:50
@@ -83,14 +83,13 @@
 	;	print
 	;	display
 	;	write
-	;	unknown
-	.
+	;	empty
+	;	unknown.
 
 :- type path
 	--->	root_rel(list(dir))
 	;	dot_rel(list(dir)).
 
-
 % If the term browser is called from the external debugger, the term browser
 % commands are send through the socket via terms of type external_request.
 :- type external_request 
@@ -121,30 +120,30 @@
 	;	unknown(char)
 	.
 
-parse__read_command(Prompt, Comm) -->
+parse__read_command(Prompt, Command) -->
 	util__trace_get_command(Prompt, Line),
 	{ string__to_char_list(Line, Cs) },
 	{ lexer(Cs, Tokens) },
-	( { parse(Tokens, Comm2) } ->
-		{ Comm = Comm2 }
+	( { parse(Tokens, Command2) } ->
+		{ Command = Command2 }
 	;
-		{ Comm = unknown }
+		{ Command = unknown }
 	).
 
-parse__read_command_external(Comm) -->
+parse__read_command_external(Command) -->
 	io__read(Result),
 	( { Result = ok(external_request(StringToParse)) } ->
 		{ string__to_char_list(StringToParse, Cs) },
 		{ lexer(Cs, Tokens) },
-		( { parse(Tokens, Comm2) } ->
-			{ Comm = Comm2 }
+		( { parse(Tokens, Command2) } ->
+			{ Command = Command2 }
 		;
-			{ Comm = unknown }
+			{ Command = unknown }
 		)
 	; { Result = eof } ->
-		{ Comm = quit }
+		{ Command = quit }
 	;
-		{ Comm = unknown }
+		{ Command = unknown }
 	).
 
 :- pred lexer(list(char), list(token)).
@@ -227,62 +226,66 @@
 
 :- pred parse(list(token), command).
 :- mode parse(in, out) is semidet.
-parse(Toks, Comm) :-
-	start(Toks, Comm).
+parse(Toks, Command) :-
+	( Toks = [] ->
+		Command = empty
+	;
+		start(Toks, Command)
+	).
 
 :- pred start(list(token), command).
 :- mode start(in, out) is semidet.
-start([Tok | Toks], Comm) :-
+start([Tok | Toks], Command) :-
 	( (Tok = name("help") ; Tok = (?) ; Tok = name("h")) ->
 		Toks = [],
-		Comm = help
+		Command = help
 	; (Tok = name("cd") ; Tok = (^)) ->
 		( Toks = [] ->
-			Comm = cd
+			Command = cd
 		;
 			parse_path(Toks, Path),
-			Comm = cd(Path)
+			Command = cd(Path)
 		)
 	; Tok = name("pwd") ->
 		Toks = [],
-		Comm = pwd
+		Command = pwd
 	; Tok = name("ls") ->
 		( Toks = [] ->
-			Comm = ls
+			Command = ls
 		;
 			parse_path(Toks, Path),
-			Comm = ls(Path)
+			Command = ls(Path)
 		)
 	; Tok = name("mark") ->
 		( Toks = [] ->
-			Comm = mark
+			Command = mark
 		;
 			parse_path(Toks, Path),
-			Comm = mark(Path)
+			Command = mark(Path)
 		)
 	; Tok = name("set") ->
 		( Toks = [] ->
-			Comm = set
+			Command = set
 		;
 			parse_setting(Toks, Setting),
-			Comm = set(Setting)
+			Command = set(Setting)
 		)
 	; Tok = name("quit") ->
 		Toks = [],
-		Comm = quit
+		Command = quit
 	; (Tok = name("display") ; Tok = name("d")) ->
 		Toks = [],
-		Comm = display
+		Command = display
 	; (Tok = name("write") ; Tok = name("w")) ->
 		Toks = [],
-		Comm = write
+		Command = write
 	; (Tok = name("print") ; Tok = name("p")) ->
 		Toks = [],
-		Comm = print
+		Command = print
 	;
 		Tok = (<),
 		Toks = [num(Depth)],
-		Comm = set(depth(Depth))
+		Command = set(depth(Depth))
 	).
 
 :- pred parse_path(list(token), path).
@@ -397,6 +400,8 @@
 	io__write_string("display\n").
 show_command(write) -->
 	io__write_string("write\n").
+show_command(empty) -->
+	io__write_string("empty\n").
 show_command(unknown) -->
 	io__write_string("unknown\n").
 
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