"Lecture 20, CSE341, Winter 2006"
"Introduction to Smalltalk -- Workspace based on fall 2004 demo"

4.
Transcript show: 4.
x _ true.
y := 5.
z := 1

[ y > 1 ] whileTrue: [z := z * y. y:= y - 1].
z

str := 'hi mom'.
str at: 4

str at: 4 put: $t.
str at: 4

str class

"str at: 4 put: 34"
"str at: 'huh' put: $x"
"str at: 123 put: $x"

5 negated.
4 + 9.
3 raisedTo: 4

"nil negated"
" 'hi' negated "
" [3] negated"

th := [x+y].
x:=4.
y_3.
th value.
[3] value negated

factHelp := [:x :acc |
					[x > 1] whileTrue:
				     	[acc _ acc * x.
						 x _ x - 1].
					acc].
fact := [:x | factHelp value: x value: 1].
fact2 := [:x | factHelp valueWithArguments: {x. 1}].
(fact value: 5) + (fact2 value: 4)

factcheck := [:x | x > 0 ifTrue: [fact value: x]
	                               ifFalse: [self error: 'neg arg']]
"(factcheck value: 5) + (factcheck value: -3)"

Object subclass: #MyPoint
   instanceVariableNames: 'x y'
   classVariableNames: ''
   poolDictionaries: ''
   category: 'lec20'

pt := MyPoint new
"pt x"

"nobody actually defines methods this way"
MyPoint compile: 'x ^x'.
MyPoint compile: 'x: a  x _a'

pt x.
pt x: 17.
pt x.