----- Original Message -----
From: "Hugo Duncan" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, January 29, 2003 12:23 PM
Subject: [boost] BOOST_PP_XX_INCCLUDE
> On Mon, 27 Jan 2003 12:42:14 -0800, "Paul Mensonides" <[EMAIL PROTECTED]>
wrote:
>
> > #define BOOST_PP_HEADERS \
> > (...), /* i.e. "no path" */ \
> > (iostream)(fstream)(vector)(string) \
> > (map)(cstdlib)(sstream) \
> > /**/
> >
> > ??=include BOOST_PP_ANGLED_INCLUDE()
> >
> > ....effectively does this:
> >
> > #include <iostream>
> > #include <fstream>
> > #include <vector>
> > #include <string>
> > #include <map>
> > #include <cstdlib>
> > #include <sstream>
>
> Looks good to me.
Does anyone else have any comments about what they'd like out of such a
mechanism?
> I would like to take a file that uses BOOST_PP_HEADERS, say
>
> > #define BOOST_PP_HEADERS \
> > (...), /* i.e. "no path" */ \
> > (iostream)(fstream)(vector)(string) \
> > (map)(cstdlib)(sstream) \
> > /**/
> >
> > ??=include BOOST_PP_ANGLED_INCLUDE()
>
> and preprocess it to generate the file that says
>
> > #include <iostream>
> > #include <fstream>
> > #include <vector>
> > #include <string>
> > #include <map>
> > #include <cstdlib>
> > #include <sstream>
Ah, you mean _without_ actually including the files? Well, for obvious reasons,
this can't be done without a double preprocessor pass, but it is possible. To
make such a file, you'd have to write the #include directive manually, something
like:
#include <boost/preprocessor/iteration/local.hpp>
#include <boost/preprocessor/seq/elem.hpp>
#include <boost/preprocessor/seq/size.hpp>
#define HASH #
#define HEADERS \
(iostream)(fstream)(vector)(string) \
(map)(cstdlib)(sstream) \
/**/
#define BOOST_PP_LOCAL_LIMITS \
(0, BOOST_PP_SEQ_SIZE(HEADERS) - 1) \
/**/
#define BOOST_PP_LOCAL_MACRO(n) \
HASH include <BOOST_PP_SEQ_ELEM(n, HEADERS)> \
/**/
#include BOOST_PP_LOCAL_ITERATE()
#undef HASH
#undef HEADERS
Preprocessing this will output a set of include directives:
# include <iostream>
# include <fstream>
# include <vector>
# include <string>
# include <map>
# include <cstdlib>
# include <sstream>
However, you may have problems with the pound-sign (#), so you may have to do
something more ridiculous like defining HASH like this:
#define HASH % ## :
%: is the digraph for '#' and prevents it from being a macro expansion
operator--i.e. stringizing. Of course, whatever uses the resulting file must be
able to handle digraphs. I'm not sure if this is a good solution or not, it is
dangerously close to being undefined behavior--if it isn't already. It seems to
me that it would be easier to just write it by hand, or use a small program to
write it out for you. I don't know, just some thoughts.
> > You can simply make a source file that includes all the files that you want
> > to pre-preprocess (if that is what your getting at), run it through your
> > compiler's preprocessor, and then include the result file.
>
> I don't think bjam supports just running the preprocessor, but as you say
> the poblem is more tricky; I would like to stop preprocessing at a certain
> include depth.
This I can't do without compiler support.
> > ....but this is outside the scope of the pp-lib can automate because it
> > requires a separate build step to produce the preprocessor equivalent of a
> > "pre-compiled header."
>
> I didn't mean to imply it was within scope. I know MPL does preprocessing
> using python, but I don't know how reuseable that code is, so I was
> just hunting for tips, suggestions and pointers.
>
> Thanks for your help. Look forward to seeing BOOST_PP_INCLUDE when you have
time.
I'll write up a copy and send it to you directly to try out.
Paul Mensonides
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