Would it make sense to use memoization more broadly for the definition of the factorial in the math lib, maybe with a `provide'd parameter to control how many values can be memoized? https://github.com/plt/racket/blob/master/collects/math/private/number-theory/factorial.rkt
While building big numbers (around 800!) I had to redefine my own factorial and binomial functions with memoization, otherwise it would take too long. Also, probably `binomial' could take advantage of this memoization, just like `permutations' does. https://github.com/plt/racket/blob/master/collects/math/private/number-theory/binomial.rkt Currently (in DrRacket, so not entirely accurate, but should be close enough): > (time (for ([n 100]) (binomial 10000 4000))) cpu time: 4072 real time: 4075 gc time: 440 > (time (for ([n 10000]) (binomial 800 400))) cpu time: 9424 real time: 9430 gc time: 836 > (time (for ([i 1000]) (factorial 10000))) cpu time: 11441 real time: 11630 gc time: 276 which makes it impractical in some cases. Laurent
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