version()

[Jonathan M Davis]

On Monday, January 16, 2012 02:16:03 Manu wrote:
> > As for
> > 
> > version(linux || OSX)
> > 
> > you can use
> > 
> > version(Posix)
> > 
> > It'll include FreeBSD as well, but then again, if something is common to
> > both
> > linux and OSX, then it's almost certainly in FreeBSD as well.
> 
> Fair enough, although this is just an example.
> In my current case, linux and MinGW are the same, but FreeBSD is different.
> You can't rely on predefined unions.

True. I'm just saying that in the case of

version(linux || OSX)

there is a good alternative. Personally, I would have thought that using && 
and || would be permitted, but it's not. But again, I'd have to dig through 
the archive to see what exactly Walter's arguments were except that he 
definitely thought that allowing && and || would lead to worse code. It 
probably relates to him not wanting to allow !, which I _do_ understand and 
agree with. Something like

version(Posix)
{}
else version(Windows)
{}
else
	static assert(0, "Unsupported OS");

will catch bugs and save you trouble in comparison to

version(Posix)
{}
else
{}

Yes, right now. Everything that isn't Posix may be Windows, but that won't 
necessarily always be true. So, when it comes to versioning, code should 
definitely be versioned on what it _is_ rather than what it _isn't_. But that 
doesn't preclude having && and ||. It's just an argument for disallowing !. 
And as you can see by my example, you can essentially _already_ do ! thanks to 
else.

- Jonathan M Davis