public <DD> T4<A, B, C, DD> map_4(Function<? super D, ? extends DD> fn) { return Tuple.of(_1(), _2(), _3(), fn.apply(_4())); }
public <BB> T4<A, BB, C, D> map_2(Function<? super B, ? extends BB> fn) { return Tuple.of(_1(), fn.apply(_2()), _3(), _4()); }
public <CC> T4<A, B, CC, D> map_3(Function<? super C, ? extends CC> fn) { return Tuple.of(_1(), _2(), fn.apply(_3()), _4()); }
public <AA> T4<AA, B, C, D> map_1(Function<? super A, ? extends AA> fn) { return Tuple.of(fn.apply(_1()), _2(), _3(), _4()); }