[GRASS5] r.mapcalc problem

[Glynn Clements]

Hamish wrote:

> I'm trying to use r.mapcalc from the command line, with a map name which
> contains a dash ("-"). I'm getting this error:
> 
> GRASS5.3> r.mapcalc \"a-b\"=1
> invalid map: a-b
> syntax error, unexpected '=', expecting $end
> Parse error
> 
> The "invalid map" above doesn't exist yet, if I make something called
> 'a-b', the invalid map error disappears but the syntax/parse errors
> remain.
> 
> does anyone know where I'm going wrong, or is this a r.mapcalc bug?

It's a mapcalc limitation. The documentation isn't clear on whether
this is meant to work.

> If I understand correctly, quoted map names containing operators should
> be ok on both sides of the equation..

I don't know whether they "should" be OK, but they aren't.

Currently, the LHS of an assignment has to be a NAME or VARNAME, both
of which are defined by the regexp:

		[^ ^#@,"'\000-\037()\[\]+\-*/%><!=&|?:;]+

[The difference is that a VARNAME has already occurred as the LHS of a
previous assignment, whereas a NAME hasn't.]

The syntax for map names where they occur as values (i.e. other than
on the LHS of an assignment) is more general:

	map		: STRING
			| NAME
			| NAME '@' NAME		{ $$ = composite($1,$3);	}
			;

[STRING is an arbitrary quoted string.]

The attached patch will allow quoted strings to occur on the LHS of an
assigmnent (at least from the perspective of the parser; there may be
other factors which I've overlooked).

More generally, I think that we should reconsider the behaviour of
assignment. Currently, the semantics are far from clear.

At a minimum, we should probably refactor the grammar, so that
top-level assignments (i.e. map creation) are handled separately to
variable assignments.

-- 
Glynn Clements <glynn.clements at virgin.net>

-------------- next part --------------
--- src/raster/r.mapcalc3/mapcalc.y~	Thu Apr 22 12:59:37 2004
+++ src/raster/r.mapcalc3/mapcalc.y	Thu Apr 22 13:12:54 2004
@@ -171,6 +171,7 @@
 						define_variable($$);	}
 		| VARNAME '=' exp_let	{ $$ = binding($1,$3);
 						define_variable($$);	}
+		| STRING '=' exp_let	{ $$ = binding($1,$3);		}
 		;
 
 exp		: exp_let