[ruby-talk:03554] Re: function objects?

Hi, 

This message is off topic, perhaps.  Consider as FYI :-)

In message "[ruby-talk:03541] function objects?"
    on 00/06/19, Johann Hibschman <[e-mail]> writes:
>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?

Well, I would write it without function objectization:

  Num::integrate(a, b){|x| f(x)}

because it seems to fit for physicist's notation:

  / b
  |   dx f(x)
  / a

The following shows a simple definition. 

  module Num
    def integrate(from, to, n = 1000)
      from, to = from.to_f, to.to_f
      dx = (to-from)/n
      x = from+dx/2     # mid point method
      sum = 0.0

      n.times do
        sum += yield(x)
        x += dx
      end

      return sum*dx
    end

    module_function :integrate
  end

  include Math, Num
  p integrate(0,PI/2){|x| cos(x)}  #=> 1.000000103

-- gotoken