Re: [Boost-users] Non-boost c++ novice help

From: Sebastian Redl (sebastian.redl_at_[hidden])
Date: 2006-02-16 11:23:42

Perry Smith wrote:

>If this is not an appropriate list for this question, please let me  
>know.
>  
>
It is not, but I'm going to answer the question this once.

>The books tell me to prefer const to #defines -- but where do you put  
>them to have the right scope and not take up space in the object?
>  
>
For in-class constants, you need to make them static, too.

>What I'd like to have is:
>
>class register {
>   void set_mask() { reg |= mask; }
>
>private:
>     uint64_t reg;
>const uint64_t mask = 0x12345678;
>};
>  
>
->
static const uint64_t mask = 0x12345678

Note that older compilers may not support this syntax.

>But the compiler will not let me do this and even if it did,the mask  
>would take up physical space.  I don't want mask (or reg) to be  
>visable outside of the class and I want the compiler to use mask as a  
>compile time constant that does not consume space after the compile.
>  
>
As long as you don't use mask in a context where it must take up space 
(such as taking its address), it won't.

For future reference, a better place for straight C++ questions is 
Usenet's comp.lang.c++, or if you feel more comfortable with a browser 
interface, bulletin boards such as http://cboard.cprogramming.com/ .

Sebastian Redl