[Boost-users] Spirit Attributes, Semantic Actions, and Closures: The relationship.

From: Aaron W. LaFramboise (aaronrabiddog51_at_[hidden])
Date: 2004-06-12 15:57:58

Hi,

I've been learning about Boost Spirit from the documentation, and one 
big gap I'm finding is how Spirit knows to call a particular signature 
semantic action given a particular parser.

I see this has something to do with the match type, but I'm not sure how 
to actually define the match type for rule.  I've discovered by accident 
that semantic actions seem to be called with the type of the closure 
member of a single-member closure, but I don't see this documented, and 
I can't quite figure out how its supposed to work.  Its difficult to 
deduce expected signatures by the compiler error approach because GCC is 
giving fairly nonsensical errors for the sorts of template constructs 
Spirit seems to use, when something goes wrong.

In particular, I'd like to know specifically how I am supposed to be 
defining semantic actions for my rules.  Perhaps this is something that 
would be nice to be included somewhere in the documenation.  Maybe it 
is, but I missed it somehow, or it wasn't spelled out explicitly enough 
for me to catch on.

Any help or pointers would be greatly appreciated!

(By the way, I have to repeat the almost obligatory comment that 
everyone seems to make about Spirit: it is one of the most beautiful 
examples of C++ I have ever seen!)

Aaron W. LaFramboise