Re: [boost] Re: boost::bind and the preprocessor

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2002-03-08 09:04:44

----- Original Message ----- 
From: "vesa_karvonen" <vesa_karvonen_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Friday, March 08, 2002 8:24 AM
Subject: [boost] Re: boost::bind and the preprocessor

> --- In boost_at_y..., "Peter Dimov" <pdimov_at_m...> wrote:
> [...]
> > I haven't found the 'perfect' solution to this problem yet. The
> > preprocessor library has the advantage that the preprocessor is
> > always present; but it adds a significant amount of obfuscation.
> 
> Macro definitions can be a bit difficult to read when they are mixed 
> with ordinary C++ code. Macro uses, on the other hand, are not very 
> difficult to read. Most of the macros offered by the preprocessor 
> library are rather fundamental and should not, IMHO, take a lot of 
> time to understand. Take BOOST_PP_REPEAT() for example.
> 
>   <--->
>   #define BOOST_PP_REPEAT(N,M,P)
> 
>   Repeats the macro M(I,P) for I = [0,N[.
> 
>   In other words, expands to the sequence:
> 
>     M(0,P) M(1,P) ... M(BOOST_PP_DEC(N),P)
>   <--->
> 
> I don't know how to make this any simpler. 

     M(0,P) M(1,P) ... M(N-1,P)
                         ^^^
Note: If N is 10, this will be the token 9, not 10-1.

For example:

    #define FOO(n, x)                + BOOST_PP_CAT(x, n)
    BOOST_PP_REPEAT(3, FOO, bar) =>  + bar1 + bar2 + bar3

-Dave