Is there a better way to "monkey-patch" Ruby's base classes?

Question

For a geometry library I'm writing I want to support multiplication of vectors by scalars, easy enough to do for vector * scalar by just defining the Vector#* method. However to support scalar * vector all the Fixnum#*, Bignum#* and Float#* methods have to be monkey-patched. I'm using the following code for each of these classes to accomplish that:

class Fixnum
  old_times = instance_method(:'*')

  define_method(:'*') do |other|
    case other
    when Geom3d::Vector
      Geom3d::Vector.new(self * other.dx, self * other.dy, self * other.dz)
    else
      old_times.bind(self).(other)
    end
  end
end

class Bignum
  #...
end

class Float
  #...
end

I'm wondering if there's any better way to accomplish this, or if there are any potential problems with doing this?

Answer 1

Take a look at Ruby's coerce feature.

Answer 2

You want #coerce

something like

class Geom3d::Vector
    def coerce(right_hand_side)
       self,right_hand_side
    end
end

http://corelib.rubyonrails.org/classes/Vector.html