  Arrows are a general interface for computation and an alternative to Monads
for API design. In contrast to Monad-based parallelism, we explore the use of
Arrows for specifying generalised parallelism. Specifically, we define an
Arrow-based language and implement it using multiple parallel Haskells.
  As each parallel computation is an Arrow, such parallel Arrows (PArrows) can
be readily composed and transformed as such. To allow for more sophisticated
communication schemes between computation nodes in distributed systems, we
utilise the concept of Futures to wrap direct communication.
  To show that PArrows have similar expressive power as existing parallel
languages, we implement several algorithmic skeletons and four benchmarks.
Benchmarks show that our framework does not induce any notable performance
overhead. We conclude that Arrows have considerable potential for composing
parallel programs and for producing programs that can execute on multiple
parallel language implementations.
