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[SVN r12604]
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Vesa Karvonen
2002-01-31 14:21:31 +00:00
parent f1590b8c08
commit 2261c57310
66 changed files with 495 additions and 680 deletions
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51
include/boost/preprocessor/for.hpp
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@ -13,51 +13,48 @@
* See http://www.boost.org for most recent version.
*/
/** \file
<a href="../../../../boost/preprocessor/for.hpp">Click here to see the header.</a>
*/
#include <boost/preprocessor/if.hpp>
#include <boost/preprocessor/tuple/eat.hpp>
/** Repeats I(R,X) and iterates F(R,X) while C(R,X) is true.
/** <P>Repeats I(R,X) and iterates F(R,X) while C(R,X) is true.</P>
In other words, expands to the sequence:
<P>In other words, expands to the sequence:</P>
<PRE>\verbatim
<PRE>
I(R,X) I(R,F(R,X)) I(R,F(R,F(R,X))) ... I(R,F(R,F(...F(R,X)...)))
\endverbatim</PRE>
</PRE>
The length of the sequence is determined by C(R,X).
<P>The length of the sequence is determined by C(R,X).</P>
<H3>Legend</H3>
- <B>X</B> is the current state of iteration. The state is usually a tuple.
- <B>C</B> is the condition for iteration. It must expand to a decimal integer
literal.
- <B>F</B> is the iterated macro. Note that if the state is a tuple, then
F(R,X) usually expands to a tuple of the same number of elements.
- <B>I</B> is the state instantiation macro.
- <B>R</B> is the recursion depth and should only be used as a parameter to
other macros using BOOST_PP_FOR() or for invoking BOOST_PP_FOR##R() directly.
For each macro using BOOST_PP_FOR(), there is a version of the macro,
distinguished by the R suffix, that accepts an additional recursion depth as
the first parameter. This technique is necessary to avoid recursively
expanding the same macro again, which is not permitted by the C++ preprocessor.
<UL>
<LI><B>X</B> is the current state of iteration. The state is usually a tuple.
<LI><B>C</B> is the condition for iteration. It must expand to a decimal
integer literal.
<LI><B>F</B> is the iterated macro. Note that if the state is a tuple, then
F(R,X) usually expands to a tuple of the same number of elements.
<LI><B>I</B> is the state instantiation macro.
<LI><B>R</B> is the recursion depth and should only be used as a parameter to
other macros using BOOST_PP_FOR() or for invoking BOOST_PP_FOR##R()
directly. For each macro using BOOST_PP_FOR(), there is a version of the
macro, distinguished by the R suffix, that accepts an additional
recursion depth as the first parameter. This technique is necessary to
avoid recursively expanding the same macro again, which is not permitted
by the C++ preprocessor.
</UL>
<H3>BOOST_PP_REPEAT() vs BOOST_PP_FOR()</H3>
BOOST_PP_FOR() is a generalization of BOOST_PP_REPEAT(). This means that
<P>BOOST_PP_FOR() is a generalization of BOOST_PP_REPEAT(). This means that
BOOST_PP_REPEAT() can be implemented using BOOST_PP_FOR(). Unfortunately,
BOOST_PP_FOR() is slower than BOOST_PP_REPEAT(). In addition,
BOOST_PP_REPEAT() was introduced earlier, is generally easier to use, and is
still quite useful on its own.
still quite useful on its own.</P>
<H3>2D and 3D repetition</H3>
BOOST_PP_FOR() can be used for multidimensional repetition simply by invoking
BOOST_PP_FOR##R() directly.
<P>BOOST_PP_FOR() can be used for multidimensional repetition simply by
invoking BOOST_PP_FOR##R() directly.</P>
*/
#define BOOST_PP_FOR(X,C,F,I) BOOST_PP_FOR0(X,C,F,I)