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
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
|
require 'facets/core/kernel/instance_exec'
module MultipleDispatch
class Dispatcher
def initialize(name, lists)
@name = name
@lists = lists
end
def run(you, args)
@lists.each do |list|
catch(:mismatch) do
return list.match(you, args)
end
end
begin
raise NoMethodError.new("undefined method `#{@name}' for #{you.inspect}:#{you.class}")
rescue NoMethodError => e
e.set_backtrace(e.backtrace[2..-1])
raise e
end
end
end
class ArgumentList
def initialize(required, optional, defaults, catch_all, catch_all_type, &action)
@required = required
@optional = optional
@defaults = defaults
@catch_all = catch_all
@catch_all_type = catch_all_type
@action = action
calc_arity
end
def calc_arity
@min_arity = @required.length
@max_arity = (@min_arity + @optional.length unless @catch_all)
end
def match(you, args)
throw :mismatch if args.length < @min_arity
throw :mismatch if @max_arity && @max_arity < args.length
(0...@required.length).each do |i|
if ArgumentChanger === @required[i]
args[i] = @required[i] === args[i]
else
throw :mismatch unless @required[i] === args[i]
end
end
(@required.length...[args.length, @required.length + @optional.length].min).each do |i|
if ArgumentChanger === @optional[i - @required.length]
args[i] = @optional[i - @required.length] === args[i]
else
throw :mismatch unless @optional[i - @required.length] === args[i]
end
end
(args.length - @required.length...@optional.length).each do |i|
args << @defaults[i]
end
if @catch_all
(@required.length + @optional.length...args.length).each do |i|
if ArgumentChanger === @catch_all_type
args[i] = @catch_all_type === args[i]
else
throw :mismatch unless @catch_all_type === args[i]
end
end
you.instance_exec(*(args[0, @required.length + @optional.length] << args[@required.length + @optional.length..-1]), &@action)
else
you.instance_exec(*args, &@action)
end
end
end
module ArgumentChanger
end
class PropertyDispatch
def initialize(&blk)
@blk = blk
end
def ===(arg)
@blk.call(arg)
end
end
class CastDispatch
include ArgumentChanger
def initialize(type)
@type = :"to_#{type}"
end
def ===(arg)
arg.send(@type) rescue throw :mismatch
end
def changes_argument?
true
end
end
class AndDispatch
def initialize(subterms)
@subterms = subterms
end
def ===(arg)
@subterms.each do |t|
return false unless t === arg
end
true
end
end
class OrDispatch
def initialize(subterms)
@subterms = subterms
end
def ===(arg)
@subterms.each do |t|
return true if t === arg
end
false
end
end
class DontCareDispatch
def initialize
end
def ===(arg)
true
end
end
end
if __FILE__ == $0
include MultipleDispatch
class A
def m(*args, &blk)
# Argument list 1
arg1 = ArgumentList.new([String, String], [], [], false, nil) do |s1, s2|
yield [:two_strings, s1, s2]
end
# Argument list 2
arg2 = ArgumentList.new([String, Integer], [], [], false, nil) do |s, i|
yield [:string_and_integer, s, i]
end
# Argument list 3
arg3 = ArgumentList.new([Integer, Integer, Integer], [], [], false, nil) do |i1, i2, i3|
yield [:three_integers, i1, i2, i3]
end
# Argument list 4
arg4 = ArgumentList.new([:do1, Integer], [], [], false, nil) do |_, i|
yield [:do1, i]
end
# Argument list 5
arg5 = ArgumentList.new([:do2, Integer], [], [], false, nil) do |_, i|
yield [:do2, i]
end
# Argument list 6
arg6 = ArgumentList.new([:do3, Integer], [Integer, String], [11, "extra"], false, nil) do |_, i1, i2, s|
yield [:do3, i1, i2, s]
end
# Argument list 7
arg7 = ArgumentList.new([:do4], [], [], true, Integer) do |_, args|
yield [:do4, args]
end
# Argument list 8
arg8 = ArgumentList.new([:do4], [], [], true, String) do |_, args|
yield [:do4, args]
end
# Argument list 9
arg9 = ArgumentList.new([PropertyDispatch.new { |a| :do5 === a }], [], [], false, nil) do |_|
yield [:do5]
end
# Argument list 10
arg10 = ArgumentList.new([/run/, DontCareDispatch.new], [], [], false, nil) do |i, dc|
yield [:run, i, dc]
end
# Argument list 11
arg11 = ArgumentList.new([:do6, CastDispatch.new(:sym)], [], [], false, nil) do |_, s|
yield [:do6, s]
end
# Dispatcher
d = Dispatcher.new(:'test', [arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11])
d.run(self, args)
end
end
A.new.m("hello", "world") { |a| p a }
A.new.m("world", 1) { |a| p a }
A.new.m(1, 2, 3) { |a| p a }
A.new.m(:do1, 1) { |a| p a }
A.new.m(:do2, 2) { |a| p a }
A.new.m(:do3, 3, 4, "a1") { |a| p a }
A.new.m(:do3, 3, 4) { |a| p a }
A.new.m(:do3, 3) { |a| p a }
A.new.m(:do4) { |a| p a }
A.new.m(:do4, 2) { |a| p a }
A.new.m(:do4, 2, 3) { |a| p a }
A.new.m(:do4, "2", "3") { |a| p a }
A.new.m(:do5) { |a| p a }
A.new.m("grunt", 1) { |a| p a }
A.new.m("grunt", :a) { |a| p a }
A.new.m(:do6, "hi") { |a| p a }
end
|
