; CONDITIONAL EVALUATION   (IF and COND)
; synatax of IF
; (if TEST TRUE-EXP FALSE-EXP)
; what this tells the Dr. Scheme is "if the TEST is true then return the TRUE-EXP, 
; otherwise return the FALSE-EXP"
; example:

(if (even? 6)
    "six is even"
    "the computer is broken")

; note that the TEST is almost always in partenthesis because it is a call to a boolean 
; procedure

(define is-input-even
 (lambda (x)
   (if (even? x) 
      "x is even"
   "x is not even")))

; COND syntax:
; (cond  
;   (TEST1 RESULT1)
;   (TEST2 RESULT2)
;   ....
;   (else  ELSE-RESULT))
; this will return the first result corresponding to a true test
; not again that tests will usuaully be boolean expressions

(define larger
  (lambda (a b)
    (cond
      ((> a b) "a is larger")
      ((> b a) "b is larger")
      (else "a and b are equal"))))