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typesetting/csp/aima-queens.rkt

25 lines
945 B
Racket

#lang br
(require "aima.rkt" sugar/debug)
;; queens problem
;; place queens on chessboard so they do not intersect
(define qs (for/list ([q 8]) (string->symbol (format "q~a" q))))
(define rows (range (length qs)))
(define vds (for/list ([q qs])
($vd q (range (length qs)))))
(define (q-col q) (string->number (string-trim (symbol->string q) "q")))
(define cs (for*/list ([qs (in-combinations qs 2)])
(match-define (list qa qb) qs)
(match-define (list qa-col qb-col) (map q-col qs))
($constraint
(list qa qb)
(λ (qa-row qb-row)
(and
(not (= (abs (- qa-row qb-row)) (abs (- qa-col qb-col)))) ; same diagonal?
(not (= qa-row qb-row)))))))
(define queens (make-csp vds cs))
(current-solver min-conflicts)
(time-named (solve queens))