Frequently when trying to implement missing language-features in
the library, it grinds to a halt because it's not possible to
send declarations as template parameters.
i.e. ex!(int i);
Phobos solved this in a for me very undesirable way, ex:
mixin(bitfields!(uint, "x", 1));
It no longer looks like a D-style declaration.
The obvious alternative is using strings and while I personally
actually prefer that to the multiple parameters approach, I know
a number of people who are vocally opposed to forcing library
end-users to deal with string-based api:s and they do have a
point, if only there was a better alternative?
ex!(int, "i"); // oh ze horror!
ex!q{int i}; // at least it now looks like a declaration again.
In before someone says: "Bikeshedding!"
Yes, it's just a few chars, but there's also a bigger difference,
type-safety, good error messages and you don't really want to
start parsing 'D' for something this trivial, every-time there is
a new feature you have to update your little parser, etc. Well, I
guess you could mixin the string as a declaration and then
reflect over it... maybe it's the best way, didn't try that
approach yet.
I did come up with a new(?) way though... as all the other
methods above, it has it's ups and downs... but I didn't see any
code in the wild using this method before, so I thought I'd share
it.
struct Struct
{
mixin restricted!((uint Size) => 777); // look ma, no strings!
mixin restricted!(uint Size = 777); // not working, "ideal
version"
}
A more complete motivating example at asm.dlang.org(just a quick
hack not production ready):
http://goo.gl/RSziKx
I guess it could be possible to solve using UDA:s instead...
maybe I'll try that next, just checking if I'm the only one
dreaming about "declarations as template parameters".
