Macro seq 

macro_rules! seq {
    () => { ... };
    ($sty:ty; $start:literal : $end:literal : $step:literal) => { ... };
    ($start:literal : $end:literal : $step:literal) => { ... };
    ($sty:ty; $start:expr , $end:expr , $step:expr) => { ... };
    ($start:expr , $end:expr , $step:expr) => { ... };
}

Create a sequence object

If type is not provided, then the Seq will default to i32 type