From: Daniel Sheppard <daniels@...>
Date: 2006-12-07T15:07:42+09:00
Subject: Re: [GOLF]: partitioning an array

> a.inject({}){|h,v|(h[yield(v)]||=[])<<v;h}.values

It's actually cleaner and shorter without that inject.

def group a
  h={}
  a.map{|v|(h[yield(v)]||=[])<<v}
  h.values
end

and if we're golfing here, it's (slightly) shorter to add that extra arg
and dump that yield:
  
def group a;h={};a.map{|v|(h[yield(v)]||=[])<<v};h.values;end
def group a,&b;h={};a.map{|v|(h[b[v]]||=[])<<v};h.values;end