On Sun, 15 Mar 2015 21:59:16 +0000, Charles Cooper wrote: > C++14 has: > template<class T, class... Types> constexpr T& get(tuple<Types...>& t); > Which allows you to get a member of the tuple struct by type. Is there > an idiomatic / library way to do this in D? Preferably by indexing.
why indexing? functional programming is fun!
import std.typecons : tuple;
template GetByType(Type, Tuple...) {
import std.typecons : isTuple;
static if (Tuple.length == 0)
static assert(false, Type.stringof~" not found");
else static if (Tuple.length == 1 && isTuple!(typeof(Tuple[0])))
enum GetByType = GetByType!(Type, Tuple[0].expand);
else static if (is(typeof(Tuple[0]) == Type))
enum GetByType = Tuple[0];
else
enum GetByType = GetByType!(Type, Tuple[1..$]);
}
static assert(2.5 == GetByType!(double, 1, 2.5));
static assert(2.5 == GetByType!(double, 1, 2.5, 3.1));
//static assert(2.5 == GetByType!(char, 1, 2.5, 3.1));
static assert(2.5 == GetByType!(double, std.typecons.tuple(1, 2.5)));
static assert(2.5 == GetByType!(double, std.typecons.tuple(1,2.5,3.1)));
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