count-columns.scm

(load "./transpose.scm")

(define (every? p l)
  (or (null? l)
      (and (p (car l))
           (every? p (cdr l)))))

(define (any? p l)
  (and (not (null? l))
       (or (p (car l))
           (any? p (cdr l)))))

(define (count-columns matrix)
  (define (subset? column row)
    (every? (lambda (x)
              (member x row))
            column))

  (define (subset-of-row? column)
    (any? (lambda (row)
            (subset? column row))
          matrix))

  (length (filter subset-of-row?
                  (transpose matrix))))

(load "../testing/check.scm")

(check (count-columns '((1))) => 1)
(check (count-columns '((1 2))) => 2)
(check (count-columns '((1) (2))) => 0)
(check (count-columns '((1 3 5 7) (2 5 3 4))) => 2)
(check (count-columns '((1 3 5 7) (2 5 3 7))) => 3)
(check (count-columns '((1 4 3) (4 5 6) (7 4 9))) => 1)
(check (count-columns '((1 4 3) (4 5 6) (7 3 9))) => 0)

(check-report)
(check-reset!)