Re: [boost] [PREPROCESSOR]:New sequence handler

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2005-11-05 16:11:53

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of Alex Mekhed

> Hello,
> sorry if I will be wrong, I am new to boost.
> As far as I know, BOOST_PP_SEQ_FOR_EACH_I works only with 256

The primary reason that SEQ_FOR_EACH_I only works for up to 256 elements is that
it passes the element index to the user-defined macro...

BOOST_PP_SEQ_FOR_EACH_I(macro, data, (a)(b)(c))

macro(r, data, 0, a) macro(r, data, 1, b) macro(r, data, 2, c)
               ^                    ^                    ^

...and the library cannot count higher than 256.

The seconary reason that SEQ_FOR_EACH_I only works for a limited number of
elements is that it is difficult to get access to the user-defined macro during
the sequential iteration.  That is, it isn't hard to enumerate through any
number of elements; it's another thing altogether to call a macro for each
element.  Now, I said it is difficult.  It is possible (Chaos does it), but you
have to rely a great deal on the timing of expansion order--which is nearly
impossible to support on the preprocessors of some prominent compilers that
Boost must support.

Regards,
Paul Mensonides