[Variable Scope & Qualifiers]
描述
關於 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
.
範例程式碼
const float pi = 3.14; float x; // .... x = pi * 2; // it's fine to use consts in math pi = 7; // illegal - you can't write to (modify) a constant
Tip
#define
或 const
You can use either const
或 #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.
參考
語法參考主頁面
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