Re: [boost] Re: [request] Sun and IBM users...

From: Toon Knapen (toon.knapen_at_[hidden])
Date: 2004-09-03 00:22:27

Daniel James wrote:

> Well, it's almost worked, but those BOOST_PP_TUPLE_EAT_2's should expand 
> to nothing. I guess it needs another expansion. The following might 
> work. Please can you try it out?

results in attachment.

> 
> In practice these macros will only get called from the other boost 
> macros which might cause these macros to expand fully? Paul will 
> understand this a lot better than me.
> 
> #include <boost/preprocessor/detail/split.hpp>
> #include <boost/preprocessor/punctuation/comma.hpp>
> #include <boost/preprocessor/punctuation/paren.hpp>
> #include <boost/preprocessor/tuple/eat.hpp>
> 
> #define IS_NULLARY(x) \
>     IS_NULLARY_2(BOOST_PP_SPLIT(1, IS_NULLARY_C x BOOST_PP_COMMA() 0)) \
>     /**/
> #define IS_NULLARY_2(x) x
> #define IS_NULLARY_C() \
>     ~, 1 BOOST_PP_RPAREN() \
>     BOOST_PP_TUPLE_EAT(2) BOOST_PP_LPAREN() ~ \
>     /**/
> 
> IS_NULLARY(())    // 1
> IS_NULLARY(()abc) // 1
> IS_NULLARY(+)     // 0
> IS_NULLARY(xyz)   // 0
> 
> #define IS_UNARY(x) IS_NULLARY(IS_UNARY_C x)
> #define IS_UNARY_C(a) ()
> 
> IS_UNARY((a))    // 1
> IS_UNARY((a)abc) // 1
> IS_UNARY(+)      // 0
> IS_UNARY(xyz)    // 0
> 
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#line 15 "pp.cpp"
1 BOOST_PP_TUPLE_EAT_2 ( ~ , 0)     
1 BOOST_PP_TUPLE_EAT_2 ( ~abc , 0)  
0      
0    
#line 23
1 BOOST_PP_TUPLE_EAT_2 ( ~ , 0)     
1 BOOST_PP_TUPLE_EAT_2 ( ~abc , 0)  
0       
0