Lisp SICP的一个程序

#lang racket(define (square x) (* x x))(define (good-enough? guess x)  (< (abs (- (square guess) x)) 0.01))(good-enough? 0.11 0.01)(define (average x y) (/ (+ x y) 2))(define (improve guess x)  (average guess (/ x guess)))(define (sqr guess x)  (if (good-enough? guess x)      guess  (sqr (improve guess x)        x)))(sqr 3 4)

关于平方开根的程序

#lang racket(define (pisum a b)  (if (> a b)      0      (+ (/ (* a (+ a 2))) (pisum (+ a 1) b))))(pisum 9 11)

这是个求pi的LISP代码

Lisp中的lambda求值：

#lang racket(define (square x) (* x x))((lambda (x y z) (+ x y (square z))) 1 2 3)((lambda (x) (+ x 4)) 5)(define plus4 (lambda (x) (+ x 4)))(plus4 3)

看完以上例子基本上对Lisp的lambda求值有比较深刻的了解了。

#lang racket(define (sum term a next b)  (if (> a b)      0      (+ (term a)          (sum term (next a) next b))))(define (inc n) (+ n 1))(define (cube x) (* x x x) )(define (sum-cube a b)  (sum cube a inc b))(sum-cube 1 10)

SICP上面的一个例子

#lang racket(define (plus4 a) (+ a 4))(define plus5 (lambda(x) (+ x 5)))(plus5 5)(plus4 6)

LISP的消息传递

#lang racket(define (make-amount balance)  (define (withdraw amount)    (if (>= balance amount)        (begin (set! balance (- balance amount))               balance)        "insufficient funds"))  (define (deposit amount)    (set! balance (+ balance amount)))  (define (dispatch m)    (cond ((eq? m 'withdraw) withdraw)          ((eq? m 'deposit) deposit)          (else (error "unknow request"                       m))))  dispatch)(define acc (make-amount 100))acc((acc 'withdraw) 50)