A simple, concise implementation of Huet's algorithm. Written because
it's difficult to translate the simple prose explanations of
algorithms often adopted by the unification community to a working
piece of code. The code is documented fully in explanation.md.
An example of how higher-order unification might be used may be found
in src/Client.hs which provides a simple type-inference/checking
algorithm for a dependently typed language with Type : Type.