Re: [Boost-users] Constant floats

From: Robert Dailey (rcdailey_at_[hidden])
Date: 2007-12-11 15:01:49

Well, the namespace idea won't work either. There's certain details I
omitted because I wasn't sure if they would be directly related to the
issue. However I'll go ahead and elaborate now.

I plan to specialize the struct containing the float to determine what
'value' I want. For example:

template< typename T >
struct default_alpha;

template<>
struct default_alpha<float>
{
    static const float alpha = 1.0f;
};

template<>
struct default_alpha<unsigned char>
{
    static const unsigned char = 255;
};

So, if I have a 'color' class that takes a template parameter, like below, I
can use the above specialized structures to figure out how to default
initialize the 'a' construction parameter.

template< typename T >
class Color
{
    Color( T r, T g, T b, T a = default_alpha<T>::value );
};

Again, I wasn't sure if these new details were required from the very
beginning. Apologies for this. Thank you for everyone's continued help.

On Dec 11, 2007 1:14 AM, Roman Perepelitsa <roman.perepelitsa_at_[hidden]> wrote:

> Robert Dailey <rcdailey <at> gmail.com> writes:
> >
> >
> > I'm going to be using this float to default-initialize a construction
> > parameter. For example:
> > struct default_alpha
> > {
> >     static const float value = 1.0f;
> > };
> > class foo
> > {
> >  foo( float r, float g, float b, float a = default_alpha::value );
> > };
> >
>
> You can use constant in namespace scope:
>
> namespace default_alpha
> {
>    static const float value = 1.0f;
> }
>
> HTH,
> Roman Perepelitsa.
>
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