Stefan O'Rear wrote: | On Mon, Jun 11, 2007 at 09:43:17AM +1000, Thomas Conway wrote: : | > codeLen 127 = 0 | > codeLen 128 = 1 | > ... | > codeLen 255 = 8 | > | > Now, compiling with ghc 6.6.1 and -O3, I see that it generates a long | > chain of conditional branches. : That's deeply tied in with Num being a subclass of Eq, isn't it? Pattern matching for /non-numeric/ data constructors should be more direct, at any optimisation level, thanks to the taglessness of the STG machine. | I'd suggest learning how to hack on GHC, I get a chain of branches even | at the maximum optimization setting. Hackers are always appreciated! Such a GHC hack may have to be limited to some known, standard numeric types. User-defined numeric types may not provide anything that you can use to look up a jump table. How would an array go, as a user-level optimisation? Regards, Tom