include Data.Pattern.Prim in Data.Pattern
Simplify the wording of the documentation
Extractors, another combinator library

Almost none of the code from the Patterns library was using the fact
that it was an environment which was being carried along. This usually
means that the types overconstrain the implementation, and that there is
something more general hidden under the surface. And indeed there was!
Extractors are more general than Patterns, and also simpler.
Heterogeneous extractors

Extractors can extract heterogeneous data! Can I use this to overcome
Pattern's major limitation of requiring all pattern-variables to match
values of the same type?