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diff --git a/source/arduino/const.rst b/source/arduino/const.rst index 295b817..4a45387 100644 --- a/source/arduino/const.rst +++ b/source/arduino/const.rst @@ -1,37 +1,35 @@ +.. highlight:: cpp + .. _arduino-const: -const keyword +const Keyword ============= -The **const** keyword stands for constant. It is a variable +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 rules of -*`variable scoping <http://arduino.cc/en/Reference/Scope>`_* that -govern other variables. This, and the pitfalls of using*#define*, -makes the *const* keyword a superior method for defining constants -and is preferred over using -*`#define <http://arduino.cc/en/Reference/Define>`_*. - +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 <arduino-scope>` that govern other +variables. This, and the pitfalls of using :ref:`#define +<arduino-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 use const's in math + 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 @@ -39,17 +37,13 @@ Example **#define** or **const** ------------------------ -You can use either **const** or **#define** for creating numeric or -string constants. For -`arrays <http://arduino.cc/en/Reference/Array>`_, you will need to -use **const**. In general *const* is preferred over *#define* for -defining constants. - - - -See also: - +You can use either ``const`` or ``#define`` for creating numeric or +string constants. For :ref:`arrays <arduino-array>`\ , you will need +to use ``const``. In general, ``const`` is preferred over ``#define`` +for defining constants. -- `#define <http://arduino.cc/en/Reference/Define>`_ -- `volatile <http://arduino.cc/en/Reference/Volatile>`_ +See Also +-------- +- :ref:`#define <arduino-define>` +- :ref:`volatile <arduino-volatile>` |