SICP問題2.56
exponentiation?の定義
(define (exponentiation? x) (and (pair? x) (eq? (car x) '**)))
baseの定義
(define (base x) (cadr x))
exponentの定義
(define (exponent x) (caddr x))
make-exponentiationの定義
(define (make-exponentiation b e) (cond ((=number? e 0) 1) ((=number? e 1) b) ; Web で他の人の答え見るとここはいらないっぽい ((and (number? b) (number? e)) (expt b e)) (else (list '** b e))))
上記定義を追加した deriv
(define (deriv exp var) (cond ((number? exp) 0) ((variable? exp) (if (same-variable? exp var) 1 0)) ((sum? exp) (make-sum (deriv (addend exp) var) (deriv (augend exp) var))) ((product? exp) (make-sum (make-product (multiplier exp) (deriv (multiplicand exp) var)) (make-product (deriv (multiplier exp) var) (multiplicand exp)))) ((exponentiation? exp) (make-product (make-product (exponent exp) (make-exponentiation (base exp) (make-sum (exponent exp) -1))) (deriv (base exp) var))) (else (error "unknown expression type -- DERIV" exp))))