reorganized all the arduino/ docs into a lang/ subdirectory since

they're properly CC attributed now.

1 files changed, 52 insertions, 0 deletions

diff --git a/source/lang/const.rst b/source/lang/const.rst
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+.. highlight:: cpp
+
+.. _lang-const:
+
+const Keyword
+=============
+
+The ``const`` keyword stands for "constant". It is a variable
+*qualifier* that modifies the behavior of the variable, making a
+variable "*read-only*". This means that the variable can be used just
+as any other variable of its type, but its value cannot be
+changed. You will get a compiler error if you try to assign a value to
+a ``const`` variable.
+
+Constants defined with the ``const`` keyword obey the same rules of
+:ref:`variable scoping <lang-scope>` that govern other
+variables. This, and the pitfalls of using :ref:`#define
+<lang-define>`, often makes using the ``const`` keyword a superior
+method for defining constants than ``#define``.
+
+Example
+-------
+
+::
+
+    // this defines a variable called "pi", which cannot be changed:
+    const float pi = 3.14;
+    float x;
+
+    // ....
+
+    x = pi * 2;    // it's fine to find the value of a const variable
+
+    pi = 7;        // illegal - you can't write to (modify) a constant
+
+
+**#define** or **const**
+------------------------
+
+You can use either ``const`` or ``#define`` for creating numeric or
+string constants. For :ref:`arrays <lang-array>`\ , you will need
+to use ``const``. In general, ``const`` is preferred over ``#define``
+for defining constants.
+
+See Also
+--------
+
+-  :ref:`#define <lang-define>`
+-  :ref:`volatile <lang-volatile>`
+
+
+.. include:: cc-attribution.txt