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author | Marti Bolivar <mbolivar@mit.edu> | 2010-12-21 10:27:37 -0500 |
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committer | Marti Bolivar <mbolivar@mit.edu> | 2010-12-21 10:27:37 -0500 |
commit | c45bccad44187da27505cf5808424e709e3f54a1 (patch) | |
tree | 18a459a50f8d0551ba046e30462c93999d982725 /docs/source/lang/cpp/define.rst | |
parent | 84fd2532a7f23d20354ff590790b3f892cb7e7d7 (diff) | |
parent | d5ad2a27f4e69e6cc9324331945937c983c30366 (diff) | |
download | librambutan-c45bccad44187da27505cf5808424e709e3f54a1.tar.gz librambutan-c45bccad44187da27505cf5808424e709e3f54a1.zip |
Merge branch 'master' into debug-serialusb.
Chose debug-serialusb version in cases of conflict.
Conflicts:
libmaple/usb/usb_callbacks.c
Diffstat (limited to 'docs/source/lang/cpp/define.rst')
-rw-r--r-- | docs/source/lang/cpp/define.rst | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/docs/source/lang/cpp/define.rst b/docs/source/lang/cpp/define.rst new file mode 100644 index 0000000..677390d --- /dev/null +++ b/docs/source/lang/cpp/define.rst @@ -0,0 +1,56 @@ +.. highlight:: cpp + +.. _lang-define: + +``#define`` +=========== + +``#define`` is a useful C and C++ feature that allows the programmer +to give a name to a constant value before the program is compiled. +The compiler will replace references to these constants with the +defined value at compile time. + +This can have some unwanted side effects. In general, the :ref:`const +<lang-const>` keyword is preferred for defining constants. + + +Syntax +------ + +The following line would define the name ``MY_CONSTANT`` to have value +``value``:: + + #define MY_CONSTANT value + +Note that the ``#`` is necessary. It is usually good style for the +name to be capitalized, although this is not required. + +There is no semicolon after the #define statement. If you include one, +the compiler will likely throw cryptic errors in unrelated places. +That is, **don't do this**:: + + // DON'T DO THIS! THE SEMICOLON SHOULDN'T BE THERE! + #define NAME value; + +Similarly, including an equal sign after the ``#define`` line will +also generate a cryptic compiler error further down the page. That +is, **don't do this, either**:: + + // DON'T DO THIS, EITHER! THE EQUALS SIGN SHOULDN'T BE THERE! + #define NAME = value + +Example +------- + +:: + + #define LED_PIN 13 + // The compiler will replace any mention of LED_PIN with + // the value 3 at compile time. + +See Also +-------- +- :ref:`const <lang-const>` + + +.. include:: cc-attribution.txt |