Creating and adding new methods in runtime

ruby-talk
1

Hello, I need to add in runtime several methods to my class. How can I
accomplish this in ruby?
More precisely: I need my class to overload arithmetic operators with
fixnums in both ways (4+MyClass, MyClass+4). All the necessary info is
stored in a hash, so I created a method to do all the stuff. It looks
like do_operation(operator, other)
But still I have to add every single operator overloader:
class Fixnum

  def doo_operation(operator, other)
  #...nevermind...
  end

  def +(other)
    do_operation(:+, other)
  end
  def -(other)
    do_operation(:-, other)
  end
end

can I automate it somehow?

2

konryd wrote:

Hello, I need to add in runtime several methods to my class. How can I
accomplish this in ruby?
More precisely: I need my class to overload arithmetic operators with
fixnums in both ways (4+MyClass, MyClass+4). All the necessary info is
stored in a hash, so I created a method to do all the stuff. It looks
like do_operation(operator, other)
But still I have to add every single operator overloader:
class Fixnum

  def doo_operation(operator, other)
  #...nevermind...
  end

  def +(other)
    do_operation(:+, other)
  end
  def -(other)
    do_operation(:-, other)
  end
end

can I automate it somehow?

the simplest case someone might come up with is:

module Operators

     def operation operator, other
         puts "operator #{operator} with argument #{other} called"
     end

     OPERATORS = [:+,:-,:/,:*]

     def self.included mod
         mod.instance_eval do
             OPERATORS.each do |op|
                 begin
                     instance_method(op)
                     alias_method(:"_#{op}", op)
                 rescue
                     # swallow NameError here
                 end

                 define_method op do |other|
                     # here you might want to check for 'other' class to preserve Numeric/Enumerable behaviour
                     operation op, other
                 end
             end
         end
     end

end

class Fixnum
     include Operators
end

1 + 2
1.send :"_+" ,2 # original

class A
     include Operators
end

A.new + A.new

lopex

3

Just overrode MyClass#coerce, and the numeric operators on other classes
will call coerce if they can't identify the class you're trying to
perform arithmetic. Make sure there are +,-, etc... operators on MyClass,
and make sure that they
(a) handle built-in numeric types
(b) handle MyClass+MyClass
(c) call coerce if they don't recognize the class on the right-hand side

There's more discussion of #coerce in PickAxe.

--Ken

···

On Fri, 11 May 2007 08:06:54 -0700, konryd wrote:

Hello, I need to add in runtime several methods to my class. How can I
accomplish this in ruby?
More precisely: I need my class to overload arithmetic operators with
fixnums in both ways (4+MyClass, MyClass+4). All the necessary info is
stored in a hash, so I created a method to do all the stuff. It looks
like do_operation(operator, other)
But still I have to add every single operator overloader: class Fixnum

  def doo_operation(operator, other)
  #...nevermind...
  end

  def +(other)
    do_operation(:+, other)
  end
  def -(other)
    do_operation(:-, other)
  end
end

can I automate it somehow?

--
Ken Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/