Thanks for the link to that paper! I recommend reading the section on "Top Level vs Referential Transparency" after reading this article. It argues that the tr

Thanks for the link to that paper! I recommend reading the section on "Top Level vs Referential Transparency" after reading this article. It argues that the trade-offs for absolute transparency require the programmer to define the entire world ahead of time. This trade-off is not acceptable by the authors of the paper for reasons elucidated in earlier sections and in SICP and so they demonstrate a version of EVAL whose environment allows for forward-references to top-level forms which we know is useful to writing dynamically compiled programs and decoupled modules. Every pure-FP language implementation has to make trade-offs with impure, mutable state and data. Haskell had to add the IO monad. Clojure has Var and Ref. Engineering isn't a discipline of absolutes. http://this-plt-life.tumblr.com/post/44462204757/simon-peyton-jones-adding-the-io-monad-to-haskell http://this-plt-life.tumblr.com/post/44462204757/simon-peyto...