Typenum is a Rust library for type-level numbers evaluated at compile time. It currently supports bits, unsigned integers, and signed integers.

Typenum depends only on libcore, and so is suitable for use on any platform!

For the full documentation, go here.

While typenum is divided into several modules, they are all re-exported through the crate root, so you can import anything contained herein with use typenum::whatever;, ignoring the crate structure.

You may also find it useful to treat the consts module as a prelude, perfoming a glob import.

Here is a trivial example of typenum's use:

use typenum::{Sum, Exp, Integer, N2, P3, P4};

type X = Sum<P3, P4>;
assert_eq!(<X as Integer>::to_i32(), 7);

type Y = Exp<N2, P3>;
assert_eq!(<Y as Integer>::to_i32(), -8);

For a non-trivial example of its use, see one of the crates that depends on it. The full list is here. Of note are dimensioned which does compile-time type checking for arbitrary unit systems and generic-array which provides arrays whose length you can generically refer to.

Typenum's error messages aren't great, and can be difficult to parse. The good news is that the fine folks at Auxon have written a tool to help with it. Please take a look at tnfilt.