const

Posted by On 11 / 07 / 2013 2 Comments

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 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.

 

Example

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const float pi = 3.14;

float x;

 

// ....

 

x = pi * 2;    // ここではconst定数を演算として使用できます

 

pi = 7;        // 不正です。const 定数に値を書き込むことはできません。

 

#define or const

You can use either const or #define for creating numeric or string constants. For arrays, you will need to use const. In general const is preferred over #define for defining constants.

 

See also

－ #define
－ volatile

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