Hey all, Been playing around with some code to multiply polynomials to calculate dice probabilities. Is based on a paper by Doron Zeilberger that I read years ago and can't find at the moment.
My first attempt represented polynomials as lists of coefficient/exponent pairs. I tried to make it completely functional, with no set! operations. You can see it here: https://github.com/TurtleKitty/Dice/blob/2fff16e198cb84d725c786ecc624fb9b9468e778/dice.rkt It worked, but only to a point. At 9 or 10 dice, it started blowing up the RAM in my machine. I swear I smelled smoke. It grabbed like 4G and slowed to a crawl. Knowing that the Perl and Javascript versions of this program can calculate distributions for 300 dice in the space of a heartbeat, I rewrote the thing to use vectors instead, and altered the polynomial multiplication function to use (begin) and (vector-set!): https://github.com/TurtleKitty/Dice/blob/67c2b49707132395f73b43afe111e3904b3898f2/dice.rkt It too now calculates three hundred dice without breaking a sweat, but... I feel dirty. Can anyone recommend a functional approach that won't melt my motherboard? I'm considering hashes, since they have the immutable version of hash-set that vectors seem to lack, but I thought I'd ask the experts. Thanks, turtlekitty (There might be a library for this already. This is more of an exercise for me than a utility.) ____________________ Racket Users list: http://lists.racket-lang.org/users
