Macro awint_internals::binop_for_each

macro_rules! binop_for_each {
    ($lhs:ident, $rhs:ident, $x:ident, $y:ident, $f:block) => { ... };
    ($lhs:ident, $rhs:ident, $x:ident, $y:ident, $range:block .rev() $f:block) => { ... };
    ($lhs:ident, $rhs:ident, $x:ident, $y:ident, $preloop:block, $range:block .rev() $f:block) => { ... };
}

If lhs.bw() != rhs.bw(), this returns None, otherwise f(x, y) is run on every corresponding pair of digits from first to last.