C / C++ / MFC

// constants.h
namespace constants
{
  extern const float pi;
}

// constants.cpp
#include "constants.h"

namespace constants
{
  const float pi = 3.141593;
}

// application.cpp
...
  int i = 5;
  float angle = constants::pi * i;
  // the code below won't work if you use #define 
  int* pi = &i;
...

SoMad wrote:

I personally think it is overkill to put the definition in a cpp file as long as we are talking about simple constants.

#define MAX_SIZE 42

int GetMaxSize()

Quote:

I was wondering what is the best way to set constanta in C/C++

#define MAX_SIZE 42
...

#include "header.h"

void foo(void)
{
   int array[MAX_SIZE];

   ...
}

enum {
   MAX_SIZE = 42
};
const struct {
   double pi;
   int size;
} constants = { 3.14, 42 };
double arr1[MAX_SIZE]; // ok in C and C++
double arr2[constants.size]; // ok in C++, error in C

const extern struct {
   double pi;
   int answer;
} constants = { 3.14, 42 };

con->setSchema(sTableName);