Macro monadic::rdrt_mdo

macro_rules! rdrt_mdo {
    (lift $last_nested_monad:expr                ) => { ... };
    (pure $last_expr:expr                ) => { ... };
    (guard $boolean:expr ; $($rest:tt)*) => { ... };
    (let $v:ident = $e:expr ; $($rest:tt)*) => { ... };
    (_ <- $monad:expr ; $($rest:tt)* ) => { ... };
    ($v:ident <- ask() ; $($rest:tt)* ) => { ... };
    ($v:ident <- lift_iter $iterator:expr ; $($rest:tt)* ) => { ... };
    (& $v:ident <- lift $nested_monad:expr ; $($rest:tt)* ) => { ... };
    ($v:ident <- lift $nested_monad:expr ; $($rest:tt)* ) => { ... };
    ($v:ident <- $monad:expr ; $($rest:tt)* ) => { ... };
    ($monad:expr                            ) => { ... };
}

macro for a ReaderT<'a, E, M> monad transformer with a boxed (env -> m a) where M: Monad + FromIterator. It uses the type alias Env in type annotations