learning-sicp

My embarrassing half assed SICP run.
git clone https://kaka.farm/~git/learning-sicp
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exercise-20.scm (660B)

      1 ;; Exercise 2.20
      2 
      3 (define (same-arity n . ns)
      4   (define (same-arity' n ns)
      5     (cond
      6      ((null? ns)
      7       (list n))
      8      ((or (and (even? n)
      9                (even? (car ns)))
     10           (and (odd? n)
     11                (odd? (car ns))))
     12       (cons n
     13             (same-arity' (car ns)
     14                          (cdr ns))))
     15      (else
     16       (cons n
     17             (same-arity' (cadr ns)
     18                          (cddr ns))))))
     19   (same-arity' n ns))
     20 
     21 
     22 (test-begin "2.20")
     23 (test-equal
     24     '(1 3 5 7)
     25   (same-arity 1 2 3 4 5 6 7))
     26 (test-equal
     27     '(2 4 6 8)
     28   (same-arity 2 3 4 5 6 7 8))
     29 (test-equal '(1) (same-arity 1))
     30 (test-equal '(2) (same-arity 2))
     31 (test-end "2.20")