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pair.scm
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pair.scm
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;; > (add-pair '(1 . 2) '(3 . 4) '(5 . 6))
;; '(9 . 12)
;; > (add-pair '(1 . 2) '(3 . 4))
;; '(4 . 6)
;; > (define p1 '(1 . 2))
;; > (define p2 '(3 . 4))
;; > (add-pair p1 p2)
;; '(4 . 6)
;; > (define p3 '(5 . 6))
;; > (add-pair p1 p2 p3)
;; '(9 . 12)
;; > (add-pair p1)
;; '(1 . 2)
;; > (add-pair '(1 . 2))
;; '(1 . 2)
(define-syntax add-pair
(syntax-rules ()
;; restricted to two operands:
;; ((_ p1 p2)
;; (cons (+ (car p1) (car p2))
;; (+ (cdr p1) (cdr p2))))
;; not good but works like this:
;; (add-pair (1 . 2) (3 . 4)) -> '(4 . 6)
;; (add-pair (5 . 4) (5 . 4) (8 . 3) (8 . 4)) -> '(26 . 15)
;; ((_ (a . b) ...)
;; (cons (+ a ...) (+ b ...)))
((_ p ...)
(cons (+ (car p) ...)
(+ (cdr p) ...)))
))
;;(apply proc-add-pair '((5 . 4) (5 . 4) (8 . 3) (8 . 4))) -> '(26 . 15)
(define (proc-add-pair p . more-p)
(let ((p-list (cons p more-p)))
(cons (apply + (map car p-list))
(apply + (map cdr p-list)))))