C++ learning notes - const

const

This is a type qualifier

const int bufSize = 512; //set bufSize is a coust.
bufSize = 0; //err: We can't change the value of a const object once we create it, it must be initialized.
const int i = get_size();
const int j = 42;
const int k; //err: k must be defined.

we could use

const

as a non

const

variable, except the

const

variable could not change the variable. A

const

one could be used to initialize other variable, and it obey the rules of type conversion.

By Default,

const

Object Are Local to a File

When a

const

is initialized from a compile-time constant, such as in out definition of

bufSize

before. The compiler will usually replace uses of the variable with its corresponding value during compilation. That is, the compiler has to get the variable’s initializer. When we split a program into multiple files, every file that uses the

const

must have access to its initializer. In order to see the initializer, the variable must be defined in every file that wants to use the variable,

const

variable are defined as local to the file.