In type theory, a refinement type is a type endowed with a predicate which is assumed to hold for any element of the refined type.
This library allows one to capture the idea of a refinement type
using the Refined type. A Refined p x wraps a value
of type x, ensuring that it satisfies a type-level predicate p.
A simple introduction to this library can be found here: http://nikita-volkov.github.io/refined/