Re: boost::bind and the preprocessor

From: vesa_karvonen (vesa_karvonen_at_[hidden])
Date: 2002-03-08 15:22:46

--- In boost_at_y..., "David Abrahams" <david.abrahams_at_r...> wrote:
> From: "vesa_karvonen" <vesa_karvonen_at_h...>
> > 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. 

Actually, what I really meant here was that BOOST_PP_REPEAT() is such 
a simple primitive that it should not be difficult to understand nor 
use.

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

I understand the motivation, but I want to make it obvious that there 
is something "different" going on. Passing expressions like N+1 to PP 
macros is something most PP library users seem to do when they start 
using the library.

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

I'll continue adding examples to the macros that currently don't have 
them.