import std.stdio, std.typecons;
 
/* hack for 2.042 and older compilers (February 2010)
 * present on ideone
 */
struct My_Tuple(T...)
{
    Tuple!T base;
    alias base this;
 
    this(T args) { this.base = Tuple!T(args); }
    U opIndex(U)(size_t idx) { return this.field[idx]; }
}
 
My_Tuple!T make_tuple(T...)(T args)
{
    return typeof(return)(args);
}
 
/* TESTING FUNCTION */
 
int[] foo(T...)(T args)
{
    writeln("Called foo ...");
    foreach (i, arg; args)
        writefln("    args[%d] == %s", i, arg);
    writeln("... foo end");
 
    return [ 5, 10, 15, 20 ];
}
 
/* UNPACKER */
 
auto unpack(alias fun, V...)(ref My_Tuple!V t)
{
    auto f(size_t i, U...)(U args)
    {
        static if (i == 0)
            return fun(args);
        else
            return f!(i - 1)(t[i - 1], args);
    }
    return f!(V.length)();
}
 
/* main */
 
void main()
{
    auto tup = make_tuple(
        5, 3.14f, "hello world", [ 5, 10, 15 ], [ "foo":5, "bar":10 ]
    );
 
    auto ret = unpack!foo(tup);
    writeln("retval from foo: ", ret);
}
 

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