TODO:
----------------
13/05/2015

This code was developed for a PhD thesis (see http://www.flocc.net/thesis/), rather than for public use, and so is a very preliminary proof of concept.
If you are interested in forking, using, adapting the code, please do get in touch by emailing developer@flocc.net.

- Currently no Main method/executuable exists that runs the code generator
  as it would be run by a real user. Instead, various test programs exist
  in Compiler.Tests, which test different aspects of the code.
  Therefore one should Implement new main method to call 
  the code generator to actually search for and
  generate code (rather than compare optimization search algorithms).
  One of the genetic searches in the Pffb test should be used for this.

- More code generation templates need to be implemented for the back-end.
  In particular templates are needed for large maps that won't fit in memory
  and for array-based combinator functions.

- The redistribution insertion algorithm needs to be fixed (currently
  show, and in an incosistant state - half reimplemented. This means
  fixing Compiler.Planner.InsertCasts. This needs to be re-implemented to fully
  implement algorithm 2 presented at the end of Chapter 5 of the PhD thesis. 

- The current DDL type inference algorithm (used by InsertCasts etc, 
  in Compiler.Types2) needs to be checked
  to make sure it properly conforms to the one given in Chapter 5. In particular, the
  normalization function must implement the down-arrow algorithm in Chapter 5.