CS 227 lecture -*- Outline -*-

* predicates (p. 23 ff)
** type predicates
*** the problem
	Scheme objects are of several types:
		numbers, symbols, pairs
	to make sure procedure is passed the right kind of data,
		need to be able to tell what type each argument is.
*** boolean
	#t is true
	#f is false

	no need to quote
-------------
 THE BOOLEANS

def: a boolean value is
 either true
 or     false.
def: a boolean object is
 either #t
 or     #f


def: a predicate is a function
of type
  (-> (<whatever>) boolean)
-------------
*** predicate
	procedure that asks a true/false question
	result is a boolean

*** type predicates,
	spend a little time on null?
	go quickly through the rest, giving examples
		(have them call out answers)
		use with several types
--------------
 TYPE PREDICATES

null?: (-> (datum) boolean)
pair?: (-> (datum) boolean)
number?: (-> (datum) boolean)
symbol?: (-> (datum) boolean)
boolean?: (-> (datum) boolean)
procedure?: (-> (datum) boolean)
--------------
	draw connection of these to types

** equality predicates
	tests for different types
	more specific tests are faster if they work
------------------
 EQUALITY PREDICATES

			    SPECIFIC, FAST
eq?: (-> (symbol symbol) boolean)
= : (-> (number number) boolean)

eqv? : (and
        (-> (symbol symbol) boolean)
        (-> (number number) boolean)
        (-> (boolean boolean) boolean))

equal?: (-> (datum datum) boolean)
			   GENERAL, SLOWER
-------------------
	eqv? means equal value...

* show how to play the car-cdr game
	(load "/home/cs227/homework/data/car-cdr-game-example.so")