There is a large difference between memoizable and memoized. Saying that the compiler is allowed to guess is great - I can get some speed without any effort. But say I'm not getting enough speed. So I profile the sucker, and find too much time wasted on the fibx function. Suspecting that it's not being memoized, I flip a switch to get it memoized, and suddenly I have my speed boost. Question: is there such a switch in Haskell? There definitely is in Perl 5 (use Memoize; memoize('fib');). I'm pretty sure there is in Perl 6 as well (some is flag, I bet).

That there is a teeny cost to memoizing in perl 5 seems to be less serious to me than the ability to actually control it. For example, I have a memory-intensive program that is allowed to run all night if it needs to. Turning off all memoizations is important - better to run slow than to crash with an out-of-memory error. Being able to say that a function can or cannot be memoized is, to me, very important.

In reply to Re^2: a better fibonacci subroutine by Tanktalus
in thread a better fibonacci subroutine by apotheon

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