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#lang racket
(define/contract (is-monotonic test-list)
(-> (listof exact-integer?) boolean?)
(cond [(empty? (cdr test-list)) #true]
[((car test-list) . > . (cadr test-list))
(is-monotonic-direction test-list >=)]
[((car test-list) . < . (cadr test-list))
(is-monotonic-direction test-list <=)]
[else (is-monotonic (cdr test-list))]))
(define/contract (is-monotonic-direction test-list dir)
(-> (listof exact-integer?) procedure? boolean?)
(cond [(empty? (cdr test-list)) #true]
[((car test-list) . dir . (cadr test-list))
(is-monotonic-direction (cdr test-list) dir)]
[else #false]))
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