Bowling Game Kata in Scheme

bowling.ss

#lang racket

(require
  rackunit
  rackunit/text-ui
)

(define (bowling rolls)
  (define (spare? rolls)
    (= (+ (first rolls)
          (second rolls)
       )
       10
    )
  )

  (define (strike? rolls)
    (= (first rolls)
       10
    )
  )

  (define (no-bonus? rolls)
    (< (length rolls) 3)
  )

  (define (bonus-frame? rolls)
    (< (length rolls) 2)
  )
  
  (define (frame-score rolls)
    (+ (first rolls)
       (second rolls)
       (bowling (list-tail rolls 2))
     )
  )

  (define (spare-score rolls)
        (+ (first rolls)
           (second rolls)
           (third rolls)
           (bowling (list-tail rolls 2))
        )
  )

  (define (strike-score rolls)
    (cond
      [(no-bonus? rolls)
        0
      ]
      [else
        (+ (first rolls)
           (second rolls)
           (third rolls)
           (bowling (list-tail rolls 1))
        )
      ]
    )
  )

  (cond
    [(bonus-frame? rolls)
      0
    ]
    [(strike? rolls)
      (strike-score rolls)
    ]
    [(spare? rolls)
      (spare-score rolls)
    ]
    [else
      (frame-score rolls)
    ]
  )
)


(define bowling-tests (test-suite "Bowling Game Kata"
  (check-equal? (bowling (make-list 20 '0))
                0
                "All `- -` Game"
  )
  (check-equal? (bowling (make-list 20 '1))
                20
                "All `1 1` Game"
  )
  (check-equal? (bowling (flatten (make-list 10 '(9 0))))
                90
                "All `9 -` Game"
  )
  (check-equal? (bowling (append '( 5 5 3) (make-list 17 '0)))
                16
                "One Spare Game"
  )
  (check-equal? (bowling (append '(10 5 3) (make-list 16 '0)))
                26
                "One Strike Game"
  )
  (check-equal? (bowling (make-list 21 '5))
                150
                "All `5 /` Game"
  )
  (check-equal? (bowling (make-list 12 '10))
                300
                "All `X` Game"
  )
))

(run-tests bowling-tests)