typedef: what's it good for?

[Chad J]

Walter Bright wrote:
> When I originally worked out ideas for D, there were many requests from
> the C and C++ community for a 'strong' typedef, and so I put one in D. I
> didn't think about it too much, just assumed that it was a good idea.
> 
> Now I'm not so sure. Maybe it should be removed for D2.
> 
> Does anyone use typedef's?
> 

A little.

> What do you use them for?
> 


typedef uint ColorFormat;
enum : ColorFormat
{
	RGB,
	RGBA,
	HSV,
	CMYK,
	// etc
}

Now you have an enum that is type safe but doesn't require a qualified
name to use.

void convertToFormat( SomeTextureType someTexture, ColorFormat fmt )
{
	// etc
}

void main()
{
	// ...
	auto foo = new SomeTextureType(...);

	convertToFormat(foo, 1); // Error, 1 is not a ColorFormat
	convertToFormat(foo, ColorFormat.RGBA ); // Nope
	convertToFormat(foo, RGBA); // This works.
}

Since ColorFormat is implicitly convertable to a uint, you should be
able to use it as an array index to populate tables and such too.

> Do you need them?

Not really.

It would be nice to have this kind of enum though.  I think it was even
mentioned in D con 2007 IIRC.