downs wrote:
Alex wrote:
Is it possible, using templates, tuples, or some other mechanism, to implement
named variadic arguments in D?
For example, I'd like to be able to do something like...
foo( 2, &bar, age : 10, status : "down");
and so forth.
Yes, with a small hack.
typedef int age_type;
age_type age(int i) { return cast(age_type) i; }
void foo(T...)(int i, Bar*, T t) {
// Test T for age_type here.
}
In D2 this won't be possible for much longer, since typedef is going
away. But you can fake it:
template Typedef(T, string name)
{
mixin("struct "~name~" { "~T.stringof~" x; alias x this; }");
}
mixin Typedef!(int, "age_type");
age_type age(int i) { return age_type(i); }
If you're going to use it a lot, you can even automate it further:
template NamedArg(T, string name)
{
mixin Typedef!(T, name~"_type");
mixin(name~"_type "~name~"("~T.stringof~" t) {"
~" return "~name~"_type(t); }");
}
mixin NamedArg!(int, "age");
mixin NamedArg!(string, "status");
foo(2, &bar, age(10), status("down"));
-Lars
