[Haskell-beginners] Capture the notion of invertible functions

Hi, These days I find the notion of "inverse function" might be useful, the basic idea is to keep a pair of function f and g which are the inverse functions of each other and then manipulate on this pair of functions. The detail is both on my blog post: http://javran.github.io/posts/2014-03-17-capture-the-notion-of-invertible-fu... and also code review: http://codereview.stackexchange.com/questions/44550/capture-the-notion-of-in... I think this is an interesting idea and want to share it with you. Advice and comments are welcomed and appreciated since I learn haskell through LYAH and some wiki pages and still not sure about what would be the most idiomatic way of doing it in haskell. Thanks, -- Javran (Fang) Cheng