;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-beginner-reader.ss" "lang")((modname lect02a) (read-case-sensitive #t) (teachpacks ((lib "world.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "world.ss" "teachpack" "htdp")))))
; Some sample expressions, reviewing booleans, and if:

; The signature of '>':
;  > : number number -> boolean
;
(> pi (sqrt 10))


; literal boolean:
false


; Actually, `>` can take in any number of args:
(>  10  8  6)
(>  10  8  9)

; This is analagous to +, which also can take
; in a variable number of args:
(+ 3 4 5 6)


; 'and' is a function which takes in booleans, return boolean:
;
(and (> 3 0)  (< pi (string-length "hello there"))  true)

(or false false true false)

(not (> 3 4))

(if (> 3 4) 
    "hello"
    "good-bye")

; Because 'if' returns a value like everything else,
; it can be incorporated in the middle of other expressions:
;
(* 17 (if (> 7 3) 4 5))

(+ 2 
   (if (> 7 3) 4 5)
   4)



; Converting types:
(number->string 432)