1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
\ examples and tests for objects.fs
\ written by Anton Ertl 1996-1998
\ public domain
cr object heap-new print
object class
:noname ( object -- )
drop ." undefined" ;
overrides print
end-class nothing
nothing heap-new constant undefined
cr undefined print
\ instance variables and this
object class
cell% inst-var n
m: ( object -- )
0 n ! ;m
overrides construct
m: ( object -- )
n @ . ;m
overrides print
m: ( object -- )
1 n +! ;m
method inc
end-class counter
counter heap-new constant counter1
cr
counter1 print
counter1 inc
counter1 print
counter1 inc
counter1 inc
counter1 inc
counter1 print
counter1 print
\ examples of static binding
cr undefined bind object print
: object-print ( object -- )
[bind] object print ;
cr undefined object-print
\ interface
\ sorry, a meaningful example would be too long
interface
selector add ( n object -- )
selector val ( object -- n )
end-interface foobar
counter class
foobar implementation
m: ( object -- )
this [parent] inc
n @ 10 mod 0=
if
." xcounter " this object-print ." made another ten" cr
then
;m overrides inc
m: ( n object -- )
0 do
this inc
loop
;m overrides add
m: ( object -- n )
n @
;m overrides val
end-class xcounter
object class
foobar implementation
cell% inst-var n
m: ( n object -- )
n !
;m overrides construct
m: ( object -- )
n @ .
;m overrides print
m: ( n object -- )
n +!
;m overrides add
protected
create protected1
protected
create protected2
cr order
public
create public1
cr order
\ we leave val undefined
end-class int
\ a perhaps more sensible class structure would be to have int as
\ superclass of counter, but that would not exercise interfaces
xcounter dict-new constant x
create y 3 int dict-new drop \ same as "3 int dict-new constant y"
cr
y print cr
20 x add
20 y add
x val .
\ y val . \ undefined
y print
cr
int push-order
order cr
words cr
int drop-order
order
cr
\ test override of inherited interface selector
xcounter class
m: ( object -- n )
this [parent] val 2*
;m overrides val
end-class ycounter
ycounter dict-new constant z
cr
z print cr
z val . cr
z inc
z val . cr
1 z add
z val . cr
\ test inst-value
object class
foobar implementation
inst-value N
m: ( n object -- )
this [parent] construct \ currently does nothing, but who knows
[to-inst] N
;m overrides construct
m: ( object -- )
N .
;m overrides print
m: ( object -- n )
N
;m overrides val
end-class const-int
5 const-int heap-new constant five
five print
five val 1+ . cr
.s cr
|
