[Boost-users] [PP] comma in macro expansions

From: Marc Mutz (marc_at_[hidden])
Date: 2006-03-11 13:45:35

Hi,

I'm having a problem with "free" commas in macro expansions. I want to 
generate some function declarations (and implementations) from a 
user-supplied BOOST_PP_SEQ. The function declarations use enable_if to switch 
between two sets of interfaces based on the type that shall be returned. 
Nevermind the details, I've just used a trivial enabling condition here, the 
error is the same as when using mpl::contains<sometype, Type> in the real 
code. I've stripped the problem down and attached a test file, complete with 
my documented attempts to delay expansion of the comma somehow. The 
preprocessor succeeds when the enable_if or it's two template args are put 
into (parentheses), but this is no longer valid C++, of course.

I guess I'm missing something, but I'm at the end of my Latin, as we say in 
Germany.

Thanks,
Marc

-- 
Marc Mutz -- marc_at_[hidden], mutz_at_[hidden]
Klarälvdalens Datakonsult AB, Platform-independent software solutions