[Haskell-cafe] Re: (Chaos) [An interesting toy]

[Simon Peyton-Jones]

| Presumably changing it to resultant = foldl' (+) wouldn't help much either?

I think not.

| Seems to me there's always a tradeoff to be made between CPU time, RAM
| usage, and code size - if not other factors too. :-S But Haskell seems
| to be fairly unique in that (it looks like) it's possible to transform
| the code quite aggressively without too much difficulty. You wouldn't
| ever want to write source code for six different versions of sum, but if
| a compiler can do it automatically that's another matter. ;-)
|
| I guess I was assuming that a function like sum is "simple enough" to
| get inlined at the call site - and hence possibly optimised at that
| site. Apparently not.

There is no reason in principle why not.  It's just that GHC doesn't do it at the moment.

| By the way, is there some way of discovering what
| GHC has "really" done with your code, rather than what you "think" it's
| done?

Yes: -ddump-simpl.

Simon