Is it possible/easy in any of the compilers/interpreters to see what the results of rewriting/optimisations are? (I'm sure it is *possible*, I'm really asking if any produce simple output in a well documented format that I'm likely to understand).
Very easy in GHC. GHC does its optimisations on code in a functional language called "Core", which is a cut-down version of Haskell with explicit typing. It's quite readable (apart from the weird automatically-chosen variable names), and you can get it to dump it at various stages. Take a look at http://www.haskell.org/ghc/docs/latest/html/users_guide/options-debugging.ht... for info. You might find the following link useful for understanding what the various passes are: http://www.cse.unsw.edu.au/~chak/haskell/ghc/comm/ HTH. --KW 8-)