alt_switch.rs

macro_rules! err {
    ($i:expr, $kind: expr) => {
        IResult::Error(error_position!($kind, $i))
    };
}

macro_rules! alt_switch {
    ($i:expr, $($lhs_mac:ident ! ( $($lhs_arg:tt)* ) $(as $lhs_binding:pat)* => $rhs_mac:ident ! ( $($rhs_arg:tt)* ) |)+ _ => $def_mac:ident ! ( $($def_arg:tt)* )) => {{
        $(if let IResult::Done(i, $($lhs_binding,)* ..) = $lhs_mac ! ( $i, $($lhs_arg)* ) {
            $rhs_mac ! ( i, $($rhs_arg)* )
        } else )+ {
            $def_mac ! ( $i, $($def_arg)* )
        }
    }};
}

alt_switch!(
  char!('(') => terminated!(sub_parse, char!(')') |
  char!('!') => map!(sub_parse, Not) |
  _ => err!(ErrorKind::Alt)
);