Bye bye, fast compilation times

[Steven Schveighoffer]

On 2/6/18 2:07 PM, H. S. Teoh wrote:
> I'm not sure I'm seeing the value of using ctRegex here.  What's wrong
> with a module static runtime regex initialized by a static this()?

No, I'd rather have it initialized on first call.

> 
> And before anyone complains about initializing the regex if user code
> never actually uses it, it's possible to use static this() on an
> as-needed basis:
> 
> 	template ipRegex()
> 	{
> 		// Eponymous templates FTW!
> 		Regex!char ipRegex;
> 
> 		static this()
> 		{
> 			ipRegex = regex(`blah blah blah`);
> 		}
> 	}
> 
> 	auto isEmail(... blah blah ...)
> 	{
> 		...
> 		if (ipRegex.match(...)) ...
> 		...
> 	}
> 
> Basically, if `ipRegex` is never referenced, the template is never
> instantiated and the static this() basically doesn't exist. :-D
> Pay-as-you-go FTW!

You may not realize that this actually compiles it for ALL modules that 
use it, and the compiler puts in a gate to prevent it from running more 
than once. So you pay every time anyways (compile-time wise at least). 
It also makes any importing module now a module that defines a static 
ctor, so cycles are much more likely.

In any case, there is a PR in the works that should eliminate the need 
for regex altogether: https://github.com/dlang/phobos/pull/6129

-Steve