hexgrid: Rust Hex Grid library crate

Bart Massey

This work-in-progress crate models a hex grid as commonly used in gaming. This crate is almost entirely derived from the excellent discussion of hex grids at the Red Blob Games website. You will want to read that before trying to use this crate.

This code is currently opinionated. The crate exposes positive y (right-handed coordinates) x-z axial coordinates (as the primary coordinate type) and cube coordinates, with flat-topped hexes. Pointy-topped hexes and various other coordinate systems should probably be an option: patches welcome.

Many thanks to Amit Patel of Red Blob Games for a definitive and crystal clear exposition.