typenum-prime

This is a rust crate that provides a marker trait for compile-time primality testing of type-level integers from the typenum crate. The test is defined for all unsigned integers.

Usage

The crate is published on https://crates.io/ as typenum-prime. Add it to your Cargo.toml in the usual way.

[dependencies]
typenum-prime = "0.2"

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT) at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

I would prefer it if you included language to this effect in the commit message of your first pull request.

lib.rs:

Compile-time primality testing of typenum integers.

The current algorithm is trial division by every prime number from 2 up to next_integer_power_of_two(sqrt(n)). The default compiler recursion limit could sometimes be insufficient, depending on the magnitude of the integer being tested. When necessary, raise it using a crate attribute:

#![recursion_limit="128"]

Example

The intended use of this crate is to put a bound on type-level integer parameters so the compiler enforces their primality. For instance, you might want the number of buckets in a statically-sized hash table to always be a prime number so that hash collisions are reduced. Now you can let the compiler enforce this constraint.

pub struct StaticHashTable<K,V,N>
    where N: Prime + ArrayLength<Option<(K,V)>> {
    buckets: GenericArray<Option<(K,V)>,N>
}