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[SVN r12612]
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Vesa Karvonen
2002-01-31 21:52:46 +00:00
parent b9f6fe1795
commit 3b7418f9ce
10 changed files with 51 additions and 128 deletions
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doc/reference/cat.htm
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@ -9,50 +9,12 @@
<hr>
<H2><a name="BOOST_PP_CAT">#define BOOST_PP_CAT</a>(X,Y)</H2>
<P>Delays the catenation of X and Y.</P>
<P>Catenates X and Y after they are macro expanded.</P>
<P>For example,</P>
<PRE>
#define STATIC_ASSERT(EXPR)\
enum\
{ <a href="cat.htm#BOOST_PP_CAT">BOOST_PP_CAT</a>(static_check_,__LINE__) = (EXPR) ? 1 : -1\
};\
typedef char\
<a href="cat.htm#BOOST_PP_CAT">BOOST_PP_CAT</a>(static_assert_,__LINE__)\
[ <a href="cat.htm#BOOST_PP_CAT">BOOST_PP_CAT</a>(static_check_,__LINE__)\
]
// ...
STATIC_ASSERT(sizeof(int) <= sizeof(long));
</PRE>
<P>expands to:</P>
<PRE>
enum
{ static_check_152 = (sizeof(int) <= sizeof(long)) ? 1 : -1
};
typedef char
static_assert_152
[ static_check_152
];
</PRE>
<P>Using <a href="cat.htm#BOOST_PP_CAT">BOOST_PP_CAT</a>() above lets the PP expand the __LINE__. If the above
code would use the ## operator directly then __LINE__ would not be expanded and
the above would expand to:</P>
<PRE>
enum
{ static_check___LINE__ = (sizeof(int) <= sizeof(long)) ? 1 : -1
};
typedef char
static_assert___LINE__
[ static_check___LINE__
];
</PRE>
<H3>Example</H3>
<UL>
<LI><a href="../../example/static_assert.c">static_assert.c</a>
</UL>
<hr>