Macro machine::transitions

macro_rules! transitions {
    ($err:expr,  $ev:ident, $($state:pat => $res:expr),*) => { ... };
    ($err:expr,  $ev:ident ($($args:ident : $t:ty),*) -> $out:ty : $default:expr, $($state:pat => $b:block),*) => { ... };
}