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From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2002-06-19 21:15:40

> Cool! Is second-level recursion possible?
> Aleksey

Currently, up to fifth-level recursion is possible, and this can be expanded as
required. Though it is a lot more like 'iteration' than recursion. In any
case, the iteration mechanism should be used only when things should logically
be repeated *vertically*. The file-iteration mechanism *cannot* produce lists
that are on the same line. Likewise, macro recursion cannot produce lists that
are *not* on the same line.

So, BOOST_MPL_AUX_LIST_FACTORY_SPECIALIZATION, and other things like it, are a
logically best implemented with file-iteration. However, lists like
BOOST_MPL_LIST_PARAMETERS are best implemented with macro recursion.

BTW, in case anybody is confused, by horizontal repetition, I mean
macro-recursion that produces a list of some sort. By vertical repetition, I
mean file-iteration that produces lists *vertically* in the output of the

Paul Mensonides

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