From: Rick DeNatale <rick.denatale@...>
Date: 2007-05-03T23:27:35+09:00
Subject: Re: Array.which_long? ( I coded an extension for Array )

On 4/29/07, James Edward Gray II <james@grayproductions.net> wrote:
> On Apr 29, 2007, at 9:38 AM, David A. Black wrote:

> > 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 :-)
>
> Well, not yet:
>
> $ ruby_yarv -e 'p %w[c bb aaa].max_by { |e| e.to_s.size }'
> "aaa"

Actually  Array#max already takes a block, and the Rdoc actually uses
almost this very use case to document it:

$ qri Array#max
--------------------------------------------------------- Enumerable#max
     enum.max                   => obj
     enum.max {|a,b| block }    => obj
------------------------------------------------------------------------
     Returns the object in enum with the maximum value. The first form
     assumes all objects implement Comparable; the second uses the
     block to return a <=> b.

        a = %w(albatross dog horse)
        a.max                                  #=> "horse"
        a.max {|a,b| a.length <=> b.length }   #=> "albatross"


Harry gave a solution along these lines early on in the thread, but no
one seems to have noticed.

The observation that 1.9 is adding max_by is interesting, but it's
more a matter of syntactic sugar than the difference between sort and
sort_by since max only needs to evaluate the block once for each
element.

Now max_by is nicer since the block just needs to return the
comparison value rather than a comparison result.

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/