Re: [boost] regex_fwd.hpp?

From: Beman Dawes (bdawes_at_[hidden])
Date: 2002-03-28 10:30:43

At 06:13 AM 3/28/2002, John Maddock wrote:
 >> The boost/filesystem/directory.hpp header I'm working on has a couple 
of
 >> signatures that take "const regex &" arguments.
 >>
 >> I really don't want to #include boost/regex.hpp since many uses of the
 >> directory.hpp header will not use regex.
 >>
 >> Has there been any discussion of providing a regex_fwd.hpp header?
 >
 >Good point, there hasn't really been any discussion, but I'll look into 
it,
 >I think it should be possible - provided default template arguments on a
 >forward declaration don't trip up any compilers - I'll experiment and see
 >what happens.  Is it just boost::reg_expression (and typedefs thereof) 
that
 >you need?

The use is to have a header which supplies a declaration:

    void some_function( const boost::regex & arg );

Because the function is a minor one, used only by a few users of the 
header, I would rather include boost/regex_fwd.hpp than boost/regex.hpp.

Right now, if I include boost/regex.hpp, a test program fails to link on 
VC++ 7.0 if a regex library isn't available, even though the user program 
never uses some_function(), and contains no other regex uses.  A 
regex_fwd.hpp header should avoid that, if at all possible.

--Beman