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  • Re: Can you help me get rid of the setf?

    From B. Pym@Nobody447095@here-nor-there.org to comp.lang.lisp,comp.lang.scheme on Sat Aug 2 07:04:18 2025
    From Newsgroup: comp.lang.lisp

    andrew.baine wrote:

    I'm looping over two variables to maximize a function, returning x and
    y that maximize f. Any way to do it without the setf in the body?

    ; Here's a function you can paste to the REPL.

    (defun f (x y)
    (- (+ (* 9 x) (* 4 y))
    (* x x)
    (* y y))

    A parenthesis is missing.


    ; And here's what I'm trying to do:

    (let ((best-x -1)
    (best-y -1)
    (max nil))
    (loop :for x :below 10 :do
    (loop :for y :below 10 :do
    (let ((n (f x
    y)))
    (if (or (null max) (> n
    max))
    (setf best-x
    x
    best-y
    y
    max n)))))
    (values best-x best-y))


    Gauche Scheme

    (use util.combinations) ;; cartesian-product
    (use gauche.collection) ;; find-max

    (define (f x y)
    (- (+ (* 9 x) (* 4 y))
    (* x x)
    (* y y)))

    (find-max
    (cartesian-product (list (iota 10) (iota 10)))
    :key (cut apply f <>))

    ===>
    (5 2)

    Another solution: (4 2)


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