Template Haskell code to implement default implementations for type-class functions based on which functions are already implemented. Currently extremely crude but still fairly effective.
When defining a type class with many functions, each of which can be implemented based on arbitrary subsets of the others, the standard default-implementation concept breaks down quite badly. This library provides a system by which more complex rules can be described for choosing default implementations based on which ones the user supplies. These implementations can additionally be given "suitability scores", so that when multiple possible choices could be made, the library can choose the "best" one.