[Issue 11737] Allow optional string value for getopt switches

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=11737



--- Comment #6 from Andrej Mitrovic <andrej.mitrovich at gmail.com> 2013-12-15 12:30:23 PST ---
(In reply to comment #3)
> (In reply to comment #2)
> > I think the default argument trick is quite neat. Andrej, would you care to
> > implement it?
> 
> I'm sure he'd love to implement it, but delegate and function pointer types
> don't currently keep any information on the name or default value of their
> parameters, meaning that this is currently impossible without declaring a
> function and passing it as an alias template parameter.

getopt is a variadic template, so it's possible to extract this information:

-----
import std.traits;

void getopt(T...)(ref string[] args, T opts)
{
    static assert(ParameterDefaultValueTuple!(opts[1])[1] == "bar");
}

void main(string[] args)
{
    getopt(args,
           "log",
           (string option, string value = "bar") { });
}
-----

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