plp/scheme/scheme2.rkt

#lang racket
(define (minimum L)
  (let ((x (car L))
        (xs (cdr L)))
        (if (null? xs)
            x
            (minimum
             (cons
              (if (< x (car xs))
              x
              (car xs))
              (cdr xs))))))
(minimum '(2 2 1 4 5))

(define (minimum2 x . rest)
  (if (null? rest)
      x
      (apply minimum2
       (cons
        (if (< x (car rest))
            x
            (car rest))
            (cdr rest)))))
(minimum2 5 9 7 88 54 79)

(let ((x 0))
  (let label ()
    (when (< x 10)
      (display x)
      (newline)
      (set! x (+ x 1))
      (label))))

(let label ((x 10))
  (when (> x 0)
    (display x)
    (newline)
    (label (- x 1))))

(define (fact x)
  (define (fact-tail x accum)
    (if (= x 0)
        accum
        (fact-tail (- x 1) (* accum x))))
  (fact-tail x 1))
(fact 10)

(for-each (lambda (x)
            (display x) (newline))
          '(this is it))

(define (vector-for-each body vect)
  (let ((max (- (vector-length vect) 1)))
    (let loop ((i 0))
      (body (vector-ref vect i))
      (when (< i max)
        (loop (+ i 1))))))

(vector-for-each (lambda (x)
                   (display x) (newline))
                 #(this is it))

(eq? 'casa 'casa)
(eq? "casa" "casa")
(eqv? 2 2)
(make-vector 5 'a)
(equal? (make-vector 5 'a) (make-vector 5 'a))
(equal? (make-vector 5 'a) (make-vector 5 'b))
(eqv? (make-vector 5 'a) (make-vector 5 'a))

(case (car(cdr '(c a)))
  ((a e i o u) 'vowel)
  ((w y) 'semivowel)
  (else 'consonant))

(cond ((> 3 2) 'greater)
      ((< 1 3) 'less)
      (else 'equal))

(define (f)
  (vector 1 2 3))
(define v (f))
(vector-set! v 0 20)
(display v)

(struct being (
               name
               (age #:mutable)
               ))

(define (being-show x)
  (newline)
  (display (being-name x))
           (newline)
  (display (being-age x)))

(define james (being "James" 30))
(being-show james)
(set-being-age! james 40)
(being-show james)

(define (say-hello x)
  (if (being? x)
      (begin
        (being-show x)
        (newline)
        (display "regards")
        )
      (error "not a being" x)))
(say-hello james)

(struct may-being being
  ((alive? #:mutable)))
(define john (may-being "John" 87 #t))
(say-hello john)