From: Trans <transfire@...>
Date: 2007-08-20T05:05:34+09:00
Subject: Re: Detecting duplicates in an array, anything in the standard library ?



On Aug 19, 12:34 pm, William James <w_a_x_...@yahoo.com> wrote:
> On Aug 19, 5:38 am, Thibaut Barr�re <thibaut.barr...@gmail.com> wrote:
>
>
>
> > Hi!
>
> > Just wondering if there is something simple already built in the std
> > library to remove duplicates from an array (or an enumerable). I've
> > seen and used various approaches, like:
>
> > module Enumerable
> >   def dups
> >     inject({}) {|h,v| h[v]=h[v].to_i+1; h}.reject{|k,v| v==1}.keys
> >   end
> > end
>
> > which will give:
>
> > > %w(a b c c).dups
>
> > => ["c"]
>
> > Anything more elegant ?
>
> > cheers
>
> > Thibaut
>
> Here's a modification of a technique used by
> Simon Kroger:
>
> class Array
>   def dups
>     values_at( * (0...size).to_a - uniq.map{|x| index(x)} )
>   end
> end
>     ==>nil


Does everyone agree that #dups is the best name for this? I recently
added this to Facets as #duplicates to avoid proximity to #dup. Is
that reasonable?

(Facets already had #nonuniq, btw.)

T.