An implementation of the F^ox language.

Relevant papers are locate here:

Convenient Explicit Effects using Type Inference with Subeffects
Daan Leijen and Ross Tate 22 June 2010
http://research.microsoft.com/apps/pubs/default.aspx?id=132620

A Flexible Semantic Framework for Effects
Ross Tate, Daan Leijen, and Sorin Lerner July 2010
http://research.microsoft.com/apps/pubs/default.aspx?id=151924