The 'Par' monad offers a parallel programming API based on dataflow
programming. To use the `Par` monad, install the monad-par package,
which includes this package as a dependency. This package is an
abstract interface only. It provides a number of type clasess, but not
an implementation. The type classes separate different levels of @Par@
functionality.
WWW: https://github.com/simonmar/monad-par