Help with const

**waterborne** · 07-14-2010

I am working on a program in which I have the struct

Code:

struct molecule {
	double x;
	double y;
	double z;
	double const radius = .05;
};

When I compile with g++ without the pedantic flag everything works fine; however, if I use the pedantic flag I get the following error:

Code:

poundcake.h:34: error: ISO C++ forbids initialization of member ‘radius’
poundcake.h:34: error: making ‘radius’ static
poundcake.h:34: error: ISO C++ forbids initialization of member constant ‘radius’ of non-integral type ‘const double’

I have read that you can only use const with types int and enum. Why is this? I don't understand why it would be a bad idea to make a double const.

Also, is there any difference between writing

Code:

const int x

versus

Code:

int const x

Thanks in advance.

**laserlight** · 07-14-2010

Originally Posted by waterborne

I have read that you can only use const with types int and enum. Why is this? I don't understand why it would be a bad idea to make a double const.

Your information is either incorrect or misinterpreted. You are allowed to initialise static const integer members directly with their declaration in the class definition. For static const non-integer members, you should perform the initialisation elsewhere, e.g., in a source file. For non-static const members, of whatever type, you should perform the initialisation in a constructor (or by using an aggregate initialiser, like how you might initialise an array).

Originally Posted by waterborne

Also, is there any difference between writing

There is no real difference.

Thread: Help with const

Thread Tools

Search Thread

Display

Help with const

Similar Threads

Polynomials and ADT's

Undefined Reference Compiling Error

Drawing Program

Certain functions

Half-life SDK, where are the constants?