;; CSE 413 19wi Lecture 1
;; DrRacket interactions window demo

Welcome to DrRacket, version 7.1 [3m].
Language: racket, with debugging; memory limit: 128 MB.

> 17
17
> (+ 1 2)
3
> (+ 3 6 2 8 6 9)
34
> +
#<procedure:+>
> (+ (* 3 4) (- 5 3))
14
> (define magic 42)
> magic
42
> (/ magic 2)
21
> spell
. . spell: undefined;
 cannot reference an identifier before its definition
> (define xvii (+ 16 1))
> xvii
17
> (* xvii magic)
714
> (define (twice n) (* 2 n))
> twice
#<procedure:twice>
> (twice 21)
42
> (- (twice 21) 10)
32
> (twice (* 3 2))
12
> (define (fact n)
    (if (< n 2)
        1
        (* n (fact (- n 1)))))
> (fact 0)
1
> (fact 1)
1
> (fact 2)
2
> (fact 3)
6
> (fact 5)
120
> (fact 10)
3628800
> (fact 100)
93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000
> (fact 99)
933262154439441526816992388562667004907159682643816214685929638952175999932299156089414639761565182862536979208272237582511852109168640000000000000000000000
> (< 1 2)
#t
> (< 2 1)
#f
> (< 1 1)
#f
> (> magic xvii)
#t
> (twice 12)
24
> (define double (lambda (n) (* 2 n)))
> (double 12)
24
> (lambda (x y) (* x y))
#<procedure>
> ((lambda (x y) (- x y)) 4 3)
1
>