From: matz@... (Yukihiro Matsumoto)
Date: 1999-05-14T16:16:50+09:00
Subject: [ruby-talk:00311] Re: help: iterator..

Hi.

In message "[ruby-talk:00310] help: iterator.."
    on 99/05/14, Pros Yeboah <yeboah@tu-harburg.de> writes:

|How  do one  pass the one pass the block of an iterator recursively
|further.
|eg.
|def  foo(bar)
|if bar  <= 0; "baz"
| else  foo(bar-=1) ????   # ??? ==>  the passed iterator block
|end
|end
|
|foo is supposed to be called  with  foo(something){block}.

Hmm, there are two ways to accomplish this.

  (a) use tha passing block, like

        foo(bar-1) {|x| yield x}

  (b) use block argument to pass block.

        def foo(bar, &block)
          ...
          foo(bar-1,&block)
          ...
        end

The former is pretty ugly, but runs bit faster.  The latter is simpler
but creation of the Proc object make it slower.

|1) I don't want to use a Proc Object as a parameter.

The second one objectifies the block into the Proc object, so it may
not sufisfy you.

|2) How can one refer to the object for the iterator block ?

The block can be objectified by either:

  * calling lambda or proc or Proc.new without block within the iterator.
  * declaring block argument as formal argument of the method.

Hope this helps you (and others).
                                                matz.