Macro scan_fmt::scan_fmt

macro_rules! scan_fmt {
    ( $instr:expr, $fmt:expr, $arg1:ty, $($arg2:ty),* ) => { ... };
    ( $instr:expr, $fmt:expr, $arg1:ty ) => { ... };
}

(a,+) = scan_fmt!( input_string, format_string, types,+ )