Question

Possible Duplicate:
initialize array size from another array value

in C++

const int a[]={1,2,3,4,5}; 
int b[a[2]]; 

int main()
{
    return 0;
} 

The code is giving error in line 2;
However, if it is something like below it gives no error after compilation:

const int a=3; 
int b[a]; 

int main()
{
    return 0;
} 

Why is that? however if i define array b inside main it is alright in both the cases…

Answer 1

Because in C++ array sizes must be constant expressions, not just constant data. Array data, even though const, is not a constant expression.

Second version IS a constant expression.