What does FP do well? (was How to get functional software engineering experience?)

[Karl-Filip Faxen]

Hi!

On the performance (or not) of high level code: I'm working on a 
compiler with a strong emphasis on generating good code for 
programs written in a fairly generic style. This work is very
far from being completed, but some of the highlights of the
compiler are:

- Aggressive removal of higher-order functions, but not when functions
  are truly used as data. So everything like foldr, map, compose and
  similar user defined functions will be removed, cross module. It's
  the cross-module part that's difficult and innovative; otherwise it's
  just plain old partial evaluation.

- I plan to use deforrestation as well, but I have not decided on the
  details yet.

- Cloning for generating different versions of functions being called
  from different call sites. Eg a nonstrict function might be legal to
  optimize more aggressively if it is only called with evaluated 
  arguments.

It is going to be interesting to see how much this will give. I suspect
that part of the performance problems of (lazy) functional languages 
come from their encouraging the programmer to use linked data structures
rather than arrays and similar biases, rather than just from overhead.

Chrees,

   /kff