On Sat, 2007-03-24 at 22:19 -0700, Erick Tryzelaar wrote:
> Every time I run my parser, it always has at least one unreachable
> nonterminal. Looking at the grammar that felix generates, it's easy to
> see the problem:
>
> nonterm(_poly_3928t_6311*) elk_1 {
> -> t:TOK_TEXT
> {
> _poly_3928t_6311 *_x = new
> _poly_3928t_6311(_nt_1007_1009(FLX_FPAR_PASS ptrcompile)
> .apply(*t));
> return _x;
> }
> }
> nonterm(_poly_3928t_6311*) _nt_1007 {
> fun dup(x) { return new _poly_3928t_6311(*x); }
> fun del(x) { delete x; }
> -> t:TOK_TEXT
> {
> _poly_3928t_6311 *_x = new
> _poly_3928t_6311(_nt_1007_1009(FLX_FPAR_PASS ptrcompile)
> .apply(*t));
> return _x;
> }
> }
>
> If I read elkhound correctly, felix is generating the same nonterminal
> twice. The only difference are the two extra functions. Is this a bug?
>From memory, this problem occurs because
parse .. with ...
is an expression which itself can contain grammar productions,
quite distinct from
nonterm ...
which is a *declared* parser function. The apparent duplication
of productions is simply because they ARE duplicated in most
cases: once in the 'parse .. with' expression and once in the
'nonterm' definition.
So the difference is evident:
nonterm(_poly_3928t_6311*) elk_1 <<<<--- anonymous nonterminal
nonterm(_poly_3928t_6311*) _nt_1007 <<<<<--- declare nonterminal
This is poor design by me, but fixing it would require some
rewriting and rethinking: the parse/with expression is basically
an anonymous, top level only, grammar which can, if it likes,
call on the library of nonterminals previously defined.
--
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net
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