how to give values to a double variable in header

[subjugater]

I am writing a header in which I want to create and immediately give value to a double. What I programmed is:

#ifndef ST_1_C_MN_H
#define ST_1_C_MN_H

#include "MaterialBase.h"

class cSt_1_C_Mn: public cMaterialBase {


///////////// Data ////////////////////

private:

//density at 20C

double den20 = 54.7;

...
the rest of the header
...

The compiler output is:

./headers/St_1_C_Mn.h:38: error: floating-point literal cannot appear in a constant-expression
./headers/St_1_C_Mn.h:38: error: ISO C++ forbids initialization of member âden20â
./headers/St_1_C_Mn.h:38: error: making âden20â static
./headers/St_1_C_Mn.h:38: error: ISO C++ forbids in-class initialization of non-const static member âden20â

Can anyone tell me what the mistake is and how I can get around this. Thank you.

[Peter87]

Set the value in the constructor

[subjugater]

Peter87,

Thanks very much! It works as you suggested!

[eypros]

Yo can put it there (in the declaration that is) only if it's const (as your compiler said) so you must initialize it when declare it:
const double den20 = 54.7;

Of course this makes sense just when you are NOT going to change the value in your program at some point