Macro ordinal 

macro_rules! ordinal {
    (first $($ty:ident)?) => { ... };
    (second $($ty:ident)?) => { ... };
    (third $($ty:ident)?) => { ... };
    ($n:literal $(-)? $suffix:ident $($ty:ident)?) => { ... };
    ($n:literal . $($ty:ident)?) => { ... };
}

Creates a 1-based ordinal number. Examples:

use num_ordinal::{O32, ordinal};

let mut o: O32 = ordinal!(first);
o = ordinal!(second);
o = ordinal!(third);

// Other numbers must use the following syntax:
o = ordinal!(4-th);
// the dash can be omitted, but then a space is required to make the Rust parser happy:
o = ordinal!(4 th);
// alternatively, a dot can be written after the number:
o = ordinal!(4 .);

// When necessary, the type can be ascribed:
let o = ordinal!(5-th O32);

Note that only first, second and third can be written as a full word:

use num_ordinal::{O32, ordinal};

// doesn't compile!
let _: O32 = ordinal!(fifth);