The const modifier in C + + Note 019:c++ is a true constant

Original notes, reproduced please specify the source!

Click "Focus", attention is also a virtue ~

program One:

We know that the subscript of an array cannot be a variable and must be a definite value. To see the program in the C language:

#define a 10

int main ()

{

The first part

int c=20;

int d=10;

int arr[c+d];

Part II

int const A=20;

int const B=10;

int arr[a+b];

return 0;

}

Of course compile errors, because the array subscript cannot be a variable.

See the same program in C + +. There is no difference in C + +, where an array subscript cannot be a variable. Errors are also compiled.

procedure Two :

Continue to see the program changes in the C language:

#define a 10

int main ()

{

The first part

int c=20;

int d=10;

int arr[c+d];

Part II

int const A=20;

int const B=10;

int arr[a+b];

return 0;

}

Compile error found! The cause of the error is consistent with the change!

In other words: in C language , the const definition of a, B is not a constant! Or a variable ! so called " constant variables "!

See the same program in C + +:

int main ()

{

The first part

int c=20;

int d=10;

int arr[c+d];

Part II

int const A=20;

int const B=10;

int arr[a+b];

return 0;

}

Compile through!!!

Conclusion :

C The const modifier in + + is a true constant , and not C in variables ( Read-only ) . C+ + is determined during const-modified constants compilation.

original notes, reproduced please specify the source!

More wonderful please pay attention to the public number: programming according to Law

The const modifier in C + + Note 019:c++ is a true constant