overload

import std.conv : to;
alias f = overload!(
    (int i) => i.to!string,
    (int i, int j) => i + j,
    (double d) => d * 2);

static assert(f(1, -2) == -1);
static assert(f(1.0) == 2.0);
static assert(f(1) == "1");

enum t = tuple(1.0, 2, tuple(3.0, tuple(tuple(4, 5.0), 6), 7.0));
static assert(map!f(t) == tuple(2.0, "2", tuple(6.0, tuple(tuple("4", 10.0), "6"), 14.0)));

// apply longest argument overload
enum t1 = tuple(1.0, 2, tuple(3, 4));
static assert(map!f(t1)  == tuple(2.0, "2", 7));

enum t2 = tuple(1.0, 2, tuple(3.0, tuple(tuple(4, 5), 6), 7.0));
static assert(map!f(t2)  == tuple(2.0, "2", tuple(6.0, tuple(9, "6"), 14.0)));