On Tuesday, 28 July 2015 at 21:12:13 UTC, Johan Engelen wrote:
Hi all,
I am wondering if there is any Phobos functionality for
indexing into a list using a type. What I mean is something
like:
assert( somethingie!(float, float, double, real)(1, 22, 333)
== 1 );
assert( somethingie!(double, float, double, real)(1, 22, 333)
== 22 );
assert( somethingie!(real, float, double, real)(1, 22, 333)
== 333 );
std.typetuple.staticIndexOf (going to be moved to std.meta in
2.068) can do this together with std.typecons.tuple:
----
void main()
{
import std.typetuple: staticIndexOf;
import std.typecons: tuple;
assert(tuple(1, 22, 333)[staticIndexOf!(float, float,
double, real)] == 1);
assert(tuple(1, 22, 333)[staticIndexOf!(double, float,
double, real)] == 22);
assert(tuple(1, 22, 333)[staticIndexOf!(real, float,
double, real)] == 333);
}
----
Or if you think that's worth encapsulating in somethingie:
----
template somethingie(T, TList...)
{
auto somethingie(A...)(A args)
{
import std.typetuple: staticIndexOf;
import std.typecons: tuple;
return tuple(args)[staticIndexOf!(T, TList)];
}
}
void main()
{
assert( somethingie!(float, float, double, real)(1, 22,
333) == 1 );
assert( somethingie!(double, float, double, real)(1, 22,
333) == 22 );
assert( somethingie!(real, float, double, real)(1, 22,
333) == 333 );
}
----
