From: Levin Alexander <levin@...>
Date: 2006-02-04T01:09:26+09:00
Subject: Re: Allow additional parameters to Enumerable#inject

On 2/3/06, Robert Klemme <bob.news@gmx.net> wrote:> > I think that inject_with_state could be made fully backwards> > compatible to inject, it would be nice if inject could be changed to> > support this.  What do you think?>> You don't need to redefine Enumerable#inject for this.>> >> def count_streams(enum)> >>   enum.inject([[],nil]) {|(a, last),e|
Thanks, I was not aware that parameters can be grouped like that.
But I think that an Enumerable#inject with additional parameters wouldalso be useful for many other things, like removing duplicates:
  def remove_duplicates1(enum)    enum.inject([[], nil]) {|(arr, last),elem| arr << elem unless elem== last; [arr, elem] }[0]  end  def remove_duplicates2(enum)    enum.inject([], nil) {|(arr, elem, last| arr << elem unless elem== last; [arr, elem] }  end
The second one seems looks a lot cleaner.
> Also, I'm not sure it's a good idea to put this method in Enumerable.  Is> it really general enough?
No, it probably is not.  This was just a for small experiment (*), iwould not put this into a library.(However, it seems to be preferred to put methods into the class"where they belong" in Ruby instead of using helper classes)
Thank you,Levin

(*) <http://www.rexswain.com/benford.html>"...It showed, he said, that the overwhelming odds are that at somepoint in a series of 200 tosses, either heads or tails will come upsix or more times in a row."
  (0..10_000).select {    (0..200).map { rand 2 }.inject([[],nil]) {|(a,last),e|      if e==last then a[-1]+=1 else a << 1 end      [a,e]    }[0].partition { |e| e >= 6 }.first.empty?  }.length / 10_000.0  #=> 0.0349
"overwhelming odds" --> 97%