On Tuesday 17 Aug 2004 5:11 pm, Malcolm Wallace wrote:
It is also possible to use Wadler's garbage-collector fix for this space leak, as implemented in nhc98. P Wadler, "Fixing a Space Leak with a Garbage Collector", SP&E Sept 1987.
When the GC discovers a selector function applied to an evaluated argument, it "evaluates" the selector on-the-fly by just swizzling pointers. It needs some co-operation from the compiler to make selector functions look obvious, but that isn't too difficult.
So ghc doesn't do this (or something better)? I'm surprised because it seems like a really basic and simple feature to me. I implemented a toy FPL a few years ago and even my gc incorporated this optimisation. It's a bit strange that this should have been overlooked considering in all other respects ghc is far more sophisticated than my efforts were :-) Regards -- Adrian Hey