From: Tim Pease <tim.pease@...>
Date: 2006-12-16T02:09:15+09:00
Subject: Re: using Proc and yield

On 12/15/06, Alber Eric <alberthier@yahoo.fr> wrote:
> OK, thank you for your quick answer
>
> I will just expose what I'm trying to do : I have four differents
> methods that are yielding strings. I want to use one or the other
> depending on the context but the rest of the process is the same, so I
> wrote something like that
>
> p1 = nil
> p2 = nil
>
> # First argument handling
> case arg1
> when 1
>     p1 = Proc.new { methodI   { |s| yield s } }
> when 2
>     p1 = Proc.new { methodII  { |s| yield ("foo-" + s + "-bar") } }
> end
>
> # Second argument handling
> case arg2
> when 3
>     p2 = Proc.new { methodIII { |s| yield s } }
> when 4
>     p1 = Proc.new { methodIV  { |s| yield ("oof-" + s + "-rab") } }
> end
>
> p1.call { |i|
>     p2.call { |j|
>          process(i)
>     }
> }
>
> What I'm looking for is a sort of function pointer.
>


def p1( arg )
  yield arg
end

def p2( arg )
  yield arg
end

# First argument handling
case arg1
when 1: nil  # p1 already defined correctly
when 2
  eval %(
    def p1( arg )
      yield( "foo-" + arg + "-bar" )
    end
  )
end

# Second argument handling
case arg2
when 3: nil  # p2 already defined correctly
when 4
  eval %(
    def p1( arg )
      yield ("oof-" + arg + "-rab")
    end
  )
end

p1( arg1 ) do |i|
  p2( arg2 ) do |j|
    process(i,j)
  end
end


No need for function pointers.  Just define (or redefine) the methods
as you need them.

Blessings,
TwP