From: "David A. Black" <dblack@...>
Date: 2005-08-20T06:48:25+09:00
Subject: Re: Problem with sort!

Hi --

On Sat, 20 Aug 2005, Vance A Heron wrote:

> Hello,
> I'm having a problem using sort! to sort an array
> in which each element is an array.  I tried to generate
> a short example, and am getting different, but still
> puzzling behavior. In my real program, the error I get
> is:
>> bin/newr2r.rb:107:in `sort': comparison of Array with Array failed
>> (ArgumentError)
>
> Any help understanding this would be appreciated.
> Thanks,
> Vance
>
> Short example:
> ---
> #! /usr/bin/env ruby
>
> a = [ ["Car", "Drive"], ["Boat", "Sail"], ["Plane", "Fly"] ]
>
> puts "Original Array"
> a.each{|v| p v}
>
> puts "\nSort to new array"
> b = a.sort{ |a, b| a[0] <=> b[0] }
> b.each{|v| puts "class(#{v.class}) #{v[0]}, #{v[1]}"}
>
> puts "\nSort to self"
> a.sort!{ |a, b|  a[0] <=> b[0] }
> a.each{|v| puts "class(#{v.class}) #{v[0]}, #{v[1]}"}

Don't use the same variable name (a) for your block variables.  You're
trampling the array a.  I think that's the root of your problems.


David

-- 
David A. Black
dblack@wobblini.net