Macro lup::lup

macro_rules! lup {
    ($sum:ty : $i:tt , $($j:tt),+ by $list:expr => $body:block) => { ... };
    ($sum:ty : $i:tt in $iter:expr , $($j:tt in $iter2:expr),+ => $body:block) => { ... };
    ($sum:ty : $i:tt by $list:expr => $body:block) => { ... };
    ($sum:ty : $i:tt in $iter:expr => $body:block) => { ... };
}