/** Tuple unpacker

 *

 * Usage: myTuple.unpack!((x, y) => f(x, y));

 *

 * Arguments are bound by order; names are irrelevant.

 *

 * Based on 'tupArg' by Dukc:

 *   https://forum.dlang.org/thread/rkfezigmrvuzkztxqqxy@forum.dlang.org

 */

template unpack(alias func)

{

    import std.typecons: isTuple;

​

    auto unpack(TupleType)(TupleType tup)

        if (isTuple!TupleType)

    {

        return func(tup.expand);

    }

}

​

void main() @nogc {

​

    import std.experimental.all;

​

    const int j = 2;

    int i = 0;

    const int[3] tmp = [1, 2, 3];

​

    tmp[]

        .zip(repeat(j))

        .filter!(unpack!((x, j) => x == j))

        .map!(unpack!((x, j) => x))

        .each!((x) scope => i = x);

    assert(i == 2);

}

​