Macro haskell_bits::mdo

macro_rules! mdo {
    (
        let $p: pat = $e: expr ; $( $t: tt )*
    ) => { ... };
    (
        let $p: ident : $ty: ty = $e: expr ; $( $t: tt )*
    ) => { ... };
    (
        $p: pat =<< $e: expr ; $( $t: tt )*
    ) => { ... };
    (
        $p: ident : $ty: ty =<< $e: expr ; $( $t: tt )*
    ) => { ... };
    (
        ign $e: expr ; $( $t: tt )*
    ) => { ... };
    (
        ret<$ty: ty> $e: expr ;
    ) => { ... };
}