RE: [Boost-Users] A strange question-)

From: Sam Gentile (ManagedCode_at_[hidden])
Date: 2002-11-13 09:59:53

Aleksey is one thread - while he answers that, I'm back to the original
question of places in Boost that show effective understandable use of
partial template specialization without all these ugly macros-) Its hard
to show something like this when I have to drill into all these macros
one by one-)

 

Sam Gentile

.NET Consultant

ManagedCode_at_[hidden]

http://www.samgentile.com

http://radio.weblogs.com/0105852/

 

-----Original Message-----
From: John Maddock [mailto:john_maddock_at_[hidden]] 
Sent: Wednesday, November 13, 2002 7:05 AM
To: Boost-Users_at_[hidden]
Subject: Re: [Boost-Users] A strange question-)

 

> I went there and indeed it can't get any simpler - at least in
theory-)
> Read the document
> C:\Boost\boost_1_29_0\libs\type_traits\c++_type_traits.htm and its
quite
> simple:
>
> template <typename T>
> struct is_void
> { static const bool value = false; };
>
> template <>
> struct is_void<void>
> { static const bool value = true; };
>
>
>
>
>
> That's exactly what I want to show. So I go to the header files and
> instead:
>
> //* is a type T void - is_void<T>
>
> BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_void,T,false)
>
> BOOST_TT_AUX_BOOL_TRAIT_SPEC1(is_void,void,true)
>
>
>
> Huh? So I look in bool_trait_def.hpp:
>
> #define BOOST_TT_AUX_BOOL_TRAIT_DEF1(trait,T,C) \
>
> template< typename T > struct trait \
>
>     : mpl::bool_c< C > \
>
> { \
>
>     BOOST_TT_AUX_BOOL_TRAIT_VALUE_DECL(C) \
>
>     BOOST_MPL_AUX_LAMBDA_SUPPORT(1,trait,(T)) \
>
> }; \
>
>
>
> Argh! Why is it done like this? This makes it much more complicated
and
> unreadable than it has to be. Why are macros being used everywhere?

A very good question - Aleksey Gurtovoy refactored them like that -
Aleksey?

John Maddock
http://ourworld.compuserve.com/homepages/john_maddock/index.htm

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