[ruby-talk:03543] Re: function objects?

Johann Hibschman <[e-mail]> writes:

> I read in one of the descriptions of the language that Ruby does not
> have first-class functions.  Is this true?  And, if so, what does Ruby
> have which makes this livable?

Yes and no. A method is not an object per se, but it's easy to make a
method into a callable object:

  # Define a class with a single method
  class Dave
    def myMethod(param)
       param*param
    end
  end

  # create an instance of the class
  dave = Dave.new

  # get a method object for the method
  m = dave.method(:myMethod)

  # Now call that method
  1.upto(4) {|i| puts m.call(i)}      #-> 1 4 9 16



The key thing is that a method object must be associated with a class
instance (an object).

> As a concrete example, what would I do if I wanted a numeric
> integration function, like
> 
>   integrate(f, x_min, x_max) -> the integral of f(x)
> 
> and, say, I wanted to pass it a method of a class as the function to
> integrate?

    integrate(obj.method(:function), x_min, x_max)



Hope this makes sense.


Regards


Dave