From: Charles Steinman <acharlieblue@...>
Date: 2005-07-31T17:26:03+09:00
Subject: Re: Higher Order Functions


Nickolay Kolev wrote:
> in fruby.rb:
>
> module Functional
>
>    def Functional.every(f, lst)
>      lst.collect { |element| f(element) }
>    end
>
> end
>
> in test.rb:
>
> require 'fruby'
>
> def times_two(x)
>      x * 2
> end
>
> p Functional.every(:times_two, [1,2,3])
>
>
> And I get this:
>
> undefined method `f' for Functional:Module (NoMethodError)
>
> How do I pass the times_two function to the module method?

p Functional.every(method(:times_two), [1,2,3]

And in Functional, it would be lst.collect { |element| f.call(element)
}

Just the token ":times_two" specifies a symbol. This symbol could
represent anything -- a method, a constant, a variable, nothing at all
-- so you use #method to get the method from the current context with a
corresponding name.

As a side note, I assume you realize that this is exactly the sort of
thing blocks are for, right?