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.
Here is what I have, it is ugly but works:
/* CODE */
static import std.stdio;
static import std.typecons;
template GetByType(alias tuple_instance, member_t)
{
ref member_t GetByType() nothrow @nogc @safe {
alias tuple_t = typeof(tuple_instance);
static assert(std.typecons.isTuple!tuple_t);
enum long idx = std.typetuple.staticIndexOf!(member_t,
tuple_instance.Types);
static if(-1 != idx)
return tuple_instance[idx];
else static assert(false); //better error message
}
}
static assert(2.5 == GetByType!(std.typecons.tuple(1,2.5),
double));
static assert(2.5 == GetByType!(std.typecons.tuple(1,2.5,3.1),
double));
void main() {
auto foo = std.typecons.tuple(1,2.5);
std.stdio.writeln(GetByType!(foo, double));
}
/* CODE */
Is there a better way to do this?
