From: Brian Candler <B.Candler@...>
Date: 2008-11-27T07:35:00+09:00
Subject: [ruby-core:20132] Re: [Bug #797] bug or feature: local method ?

On Thu, Nov 27, 2008 at 03:32:18AM +0900, Francoys wrote:
> declaring variables inside a method that are accessibles to all the
> nested methods.

You can do this with closures:

  f = lambda { |a|
    x = 0
    g = lambda { |b|
      x += b
    }
    a.each { |e| g[e] }
    x
  }
  puts f[[1,2,3]]

Or else you have objects and instance variables.

> If someone have a 'rubyly correct' way's to solve my problem. I'm am
> open. But keep in mind this: Prolog is a slow langage, so every
> performance gain count !

Then I might question whether Ruby is the correct implementation platform
for Prolog, except perhaps as a learning exercise (in which case performance
isn't important)

> As who see, i am facing a real life situation where nested methods seem
> very useful and the more elegant solution.

Note that when you write

  def foo
    ... body
  end

then it's the *execution* of "def foo ... end" which creates and defines the
method foo on the object. But the body is not executed until the time when
foo is called.

Maybe a def which occurs inside a method body (or block) would have to
become an alias for

   foo = lambda { 
     ...
   }

instead. Unfortunately, this particular foo would be called using foo.call
or foo[], not foo().

Regards,

Brian.