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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|
throw :mismatch unless @required[i] === args[i]
end
(@required.length...[args.length, @required.length + @optional.length].min).each do |i|
throw :mismatch unless @optional[i - @required.length] === args[i]
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|
throw :mismatch unless @catch_all_type === args[i]
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 nil
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
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