From: dblack@...
Date: 2006-12-21T10:39:24+09:00
Subject: Re: tricky sort for happy visitors of Paris

Hi --

On Thu, 21 Dec 2006, William James wrote:

> Jos Backus wrote:
>> More generally:
>>
>> lizzy:~% irb
>> irb(main):001:0> arrondissements = ["Paris 1", "Paris 2","Paris 4", "Paris 3", "Lyon 2", "Lyon 1"]
>> => ["Paris 1", "Paris 2", "Paris 4", "Paris 3", "Lyon 2", "Lyon 1"]
>> irb(main):002:0> sorted_array = arrondissements.sort_by {|e| [e.split(" ")]}
>> => ["Lyon 1", "Lyon 2", "Paris 1", "Paris 2", "Paris 3", "Paris 4"]
>> irb(main):003:0> %                                                              lizzy:~%
>>
>> --
>> Jos Backus
>> jos at catnook.com
>
> Won't work for
>
> arrondissements = "Paris 1", "Paris 2","Paris 12", "Paris 3",
>  "Lyon 2", "Lyon 1"
>
> For the 2nd field, you need a numeric comparison.
>
> p arrondissements.sort_by {|e|  e.split.inject{|a,b| [a,b.to_i] } }

Or:

   require 'scanf'
   p @arrondissements.sort_by {|e| e.scanf("%s%d") }


David

-- 
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