Re: [Boost-users] Xpressive, symantic actions and combination enumeration

Subject: Re: [Boost-users] Xpressive, symantic actions and combination enumeration
From: Eric Niebler (eric_at_[hidden])
Date: 2009-05-06 12:51:38

Lee Simpson wrote:
> Damn. I've just implemented the whole algorithm using your suggested 
> approach, and I've come across a problem.
> I don't have a simple way to describe my dilemma, so a complex way will 
> ave to do :-/

The best way is to post source code.

> First of, I'll describe the way I have implemented your suggestion.
> First off, I utilize an expression of the form ((s1 = expr) >> 
> keep(nil[action(_,...)])) for each significant component of the expression.
<snip>

Stop right there. Are you really using nil[action(_,...)] ? In this 
context, xpressive will replace _ with the submatch corresponding to the 
subexpression to which the semantic action is attached. In this case, 
the action is attached to nil, which always matches 0 characters. So 
your action will always be passed an empty submatch. I bet that's not 
what you want. Did you intend nil[action(s1,...)] perhaps?

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com