From: "David A. Black" <dblack@...>
Date: 2007-04-30T00:03:30+09:00
Subject: Re: Array.which_long? ( I coded an extension for Array )

Hi --

On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:
> Thanks for your reply, I learned more on this thread :P
> But I have a question:
> If I have an array contain:
>   ary = [1, 12, 234, "456"]
> there has two elements which size is 3, but the longest method just returned
> one of them.
> I can't solve it :(

It depends how you want to break the tie.  Here's a way to do it where
a size tie is broken by string comparison, which is ASCII-based.  The
nonzero? method will return -1 or 1 if the two string sizes are not
equal.  If they are equal, the comparison will evaluate to zero and
nonzero? will be false -- which means the second comparison (the ASCII
one) will be executed.

I've included some tests too.

class Array
  def longest
    sort do |a,b|
      (a.to_s.size <=> b.to_s.size).nonzero? ||
      a.to_s <=> b.to_s
    end[-1]
  end
end

require 'test/unit'

class MaxTest < Test::Unit::TestCase

  def test_all_strings
    assert_equal("David", %w{ Da David Dav }.longest)
  end

  def test_all_numbers
    assert_equal(34567, [123,12345,200,34567].longest)
  end

  def test_tie
    assert_equal("David", %w{ David Alan Black }.longest)
  end

  def test_mixed
    assert_equal("David", [123, "David", 456].longest)
  end

  def test_mixed_tie
    assert_equal("David", [12345, "David", "Black", 123, 98765].longest)
  end
end


David

> 2007/4/29, David A. Black <dblack@wobblini.net>:
> >
> > Hi --
> >
> > On 4/29/07, Robert Dober <robert.dober@gmail.com> wrote:
> > > On 4/29/07, David A. Black <dblack@wobblini.net> wrote:
> > > > You're doing too much work -- let Ruby do it :-)
> > > ... for sure, but
> > > >
> > > >   class Array
> > > >     def longest
> > > >       map {|e| e.to_s }.max
> > > >     end
> > > >   end
> > > I think it is not exactly what OP wanted
> > > because %w{x aaaa}.max is "x"
> > > so I will try to comply to his needs
> > > def longest
> > >     map{ |e| [e.to_s.size, e.to_s]}.max.first
> > > end
> >
> > You're right that I was wrong (because I didn't do the .size thing),
> > but yours gives you an integer:
> >
> > ['x', 'aaaa'].longest  # => 4
> >
> > I think you'd have to reverse your array. See Harry's code too, which
> > uses a block with max.  You could also do:
> >
> >     sort_by {|e| e.to_s.size }[-1]
> >
> > (since there's no max_by :-)
> >
> >
> > David
> >
> > --
> > Upcoming Rails training by Ruby Power and Light:
> > Four-day Intro to Intermediate
> > May 8-11, 2007
> > Edison, NJ
> > http://www.rubypal.com/events/05082007
> >
> >
>
>
> --
> Taiwan Ruby Users Group:
> http://www.ruby.oss.tw/
> http://www.ruby.oss.tw/phpbb
>


-- 
Upcoming Rails training by Ruby Power and Light:
  Four-day Intro to Intermediate
  May 8-11, 2007
  Edison, NJ
  http://www.rubypal.com/events/05082007