SICP 問題 3.1
(define (make-accumulator n) (let ((sum n)) (lambda (num) (set! sum (+ sum num)) sum)))
gosh> (define A (make-accumulator 5)) A gosh> (A 10) 15 gosh> (A 10) 25
(define (make-accumulator n) (let ((sum n)) (lambda (num) (set! sum (+ sum num)) sum)))
gosh> (define A (make-accumulator 5)) A gosh> (A 10) 15 gosh> (A 10) 25