Welcome to DrScheme, version 205.
Language: Standard (R5RS).
> (if (< 3 5) 3 5)
3
> (define (min a b)
    (if (< a b) a b))
> (min 3 5)
3
> (min 7 3)
3
> (min 1 -3)
-3


> (cond ((< 3 5) 3)
        ((< 2 6) 4)
        (else 1))
3
> (define (signum x)
    (cond ((> x 0) 1)
          ((< x 0) -1)
          (else 0)))
> (signum 3)
1
> (signum -7)
-1
> (signum 0)
0

;;; Higher-order function examples

;;; -- passing functions as arguments...

> (define (double x) (* x 2))
> double
#<procedure:double>
> (double 3)
6
> (define (f g x) (g x))
> (f double 3)
6
> double
#<procedure:double>
> 


;;; -- functions as "return values"

> (define (make-addk k)
    (lambda (x) (+ k x)))
> ((make-addk 3) 5)
8
> (make-addk 3)
#<procedure:36:4>

;; Each of these three definitions of add3 are equivalent (in that 
;; add3 is defined as a function that adds 3 to its argument

;; These first two are the normal way (the first uses the shorthand)
> (define (add3 x) (+ x 3))
> (define add3 (lambda (x) (+ x 3)))

;; This uses the make-addk function that returns a function
> (define add3 (make-addk 3))

> (add3 5)
8