Re: Non-greedy wildcard possible? (Long)

[Frank Heckenbach]

Laurence Finston wrote:

> I had a problem that reminds me of this.  Sometimes, one would like to
> "get out of" a rule in `yyparse()' and "get into" another rule.  I
> believe this to be impossible, except with `gotos', which is risky.
> If one does it, then one must be very careful about using the semantic
> values of the tokens of all the rules involved.  I _don't_ recommend
> it.

If you mean a `goto' from one action into another, this will
certainly not work. The actions in `{ ... }' are just for the
semantic values and irrelevant for the actual parsing.

What you achieve is at best to execute a part of another semantic
action, and at worst to mess up completely, especially if the code
after the `goto' accesses any `$n' values. But the parsing will
continue with the original state (it will not even notice the
`goto'). (You could try modifying the parser's internal structures,
but before you start this, you should really try to restructure your
grammar or use a more powerful parsing algorithm, i.e. GLR.)

(This is quite different from a recursive descent parser ... where a
`goto' into another rule will also mess up -- but for different
reasons. :-)

Frank

-- 
Frank Heckenbach, address@hidden
http://fjf.gnu.de/
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