Re: static constants in a class

Leigh Johnston <>
Thu, 15 Sep 2011 22:54:46 +0100
On 15/09/2011 22:32, Ian Collins wrote:

On 09/16/11 09:24 AM, Christopher wrote:

On Sep 15, 4:17 am, Ian Collins<> wrote:

On 09/15/11 08:50 PM, Alain Ketterlin wrote:

Urs Thuermann<> writes:

How should one define a constant, say of type int, in a class? The
only way that worked for me in all cases is to delcare the constant in
the class in the header file and define its value in the
implementation file:

---- foo.hh ----
class Foo {
static const int N;
---- ----
#include "foo.hh"
const int Foo::N = 10;


Make it a inline static method:

class Foo {
inline static int N() { return 10; }

The inline is unnecessary, but even without it the solution isn't valid:
Foo::N() isn't a compile time constant.

Where did the OP require it to be a _compile_ time constant?

---- ----
void f() {
int array[N];
for (int i = 0; i < N; i++) { ... }

I do not understand the template solution proposed, what are the
internal workings that make it advantagous?

It was unnecessarily complex.

Not unnecessary if you want a header file only solution to a problem; my
XML library is a header file only library but it doesn't have to
explicitly take advantage of the template trick for defining constants
as it is already composed of class templates.


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