CPP

c++ define constant in class header

class Foo
{
public:
    const int a = 5; // Valid use of const.
    constexpr int b = 7; // Invalid use of constexpr, won't even compile!
    static constexpr int c = 10; // Valid use of constexpr.

    int arrA[a]; // ERROR: 'a' is defined at runtime, so you can't use it to define a size.
    int arrB[b]; // ERROR: You couldn't even define 'b', so this is not going to work...
    int arrC[c]; // VALID: 'c' is known by the compiler, and is guaranteed to only ever be 10!
}

c++ define constant

#include <iostream>
using namespace std;

#define PI 3.14159
#define NEWLINE '
'

int main ()
{
  double r=5.0;               // radius
  double circle;

  circle = 2 * PI * r;
  cout << circle;
  cout << NEWLINE;

}
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