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# By definition a Functor is simply a first class method, but these are common
# in the form of Method and Proc. So for Ruby a Functor is a more specialized
# as a Higher-order function or Metafunction. Essentally, a Functor can vary
# its behavior accorrding to the operation applied to it.
#
# f = Functor.new { |op, x| x.send(op, x) }
# (f + 1) #=> 2
# (f + 2) #=> 4
# (f + 3) #=> 6
# (f * 1) #=> 1
# (f * 2) #=> 4
# (f * 3) #=> 9
#
class Functor #< BasicObject
EXCEPTIONS = [:binding, :inspect, :object_id]
if defined?(::BasicObject)
EXCEPTIONS.concat(::BasicObject.instance_methods)
EXCEPTIONS.uniq!
EXCEPTIONS.map!{ |m| m.to_sym }
end
#
alias :__class__ :class
## If Functor were built-in to Ruby this would not be
## needed since exceetions could just be added directly.
##$FUNCTOR_EXCEPTIONS ||= [:binding, :undefine_method]
## TODO: This will not work when BasicObject is utilized. How to fix?
##def self.honor_exceptions
## $FUNCTOR_EXCEPTIONS.each{ |name|
## next if method_defined?(name)
## eval %{
## def #{name}(*a,&b)
## super(*a, &b)
## end
## }
## }
##end
# Privatize all methods except vital methods and #binding.
instance_methods(true).each do |m|
next if m.to_s =~ /^__/
next if EXCEPTIONS.include?(m.to_sym)
undef_method(m)
end
#
def initialize(&function)
@function = function
end
#
def to_proc
@function
end
##def inspect
## #"#<Functor:#{object_id} #{method_missing(:inspect)}>" # hex id ?
## "#{method_missing(:inspect)}"
##end
## Needed?
##def send(op, *a, &b)
## method_missing(op, *a, &b)
##end
private
# Any action against the functor is processesd by the function.
def method_missing(op, *args, &blk)
@function.call(op, *args, &blk)
end
end
# Copyright (c) 2004 Thomas Sawyer (Ruby License)
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6 entries across 5 versions & 1 rubygems