XPost: comp.lang.scheme

Frank Buss <fb@frank-buss.de> writes:

Looks like you are searching for a functional way of doing this. In Haskell you could write it like this (I'm a Haskell newbie, I'm sure this can be written better, but at least it works)

f (x,y) = 9*x + 4*y - x*x - y*y
best = foldr1 max values
where values = [(f(x,y), (x,y)) | x<-[0..9], y<-[0..9]]
max t1 t2 = if (fst t1) >= (fst t2) then t1 else t2

let f x y = 9*x+4*y-x*x-y*y in
foldl1' max [(f x y,(x,y)) | x <- [0..9], y<-[0..9]]

is a little simpler. Uses the max built-in and foldl1' which operates
left to right and is strict.

Gauche Scheme

(use gauche.collection)
(use util.combinations)

(let1 f (^(x y) (+ (* 9 x) (* 4 y) (* x (- x)) (* y (- y))))
(find-max
(map (^x (list (apply f x) x))
(cartesian-product (list (iota 10) (iota 10))))
:key car))

(24 (5 2))

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