From: James Edward Gray II <james@...>
Date: 2005-10-11T06:53:25+09:00
Subject: Re: Sort pseudo-lists

On Oct 10, 2005, at 4:46 PM, pete boardman wrote:

> Say I've got a string like this:
>
> "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4, 2.2}, {1.4, 2.2, 2.1, 4.2}}"
>
> - imagine it's aspiring to be a list of sublists, with 4 reals in  
> each list. I want to produce a sorted version:
>
> (1.4    2.2    2.1    4.2)
> (2.1    3.14  2.4    2.2)
> (3.1    1.3    2.5    2.1)
>
> What would be a good way to do this?

Well, if you can count on the data format, the following is pretty  
simple:

irb(main):001:0> arr = eval "{{3.1, 1.3, 2.5, 2.1}, {2.1, 3.1, 2.4,  
2.2}, {1.4, 2.2, 2.1, 4.2}}".tr("{}", "[]")
=> [[3.1, 1.3, 2.5, 2.1], [2.1, 3.1, 2.4, 2.2], [1.4, 2.2, 2.1, 4.2]]
irb(main):002:0>
irb(main):003:0* arr.sort { |a, b| a.first <=> b.first }
=> [[1.4, 2.2, 2.1, 4.2], [2.1, 3.1, 2.4, 2.2], [3.1, 1.3, 2.5, 2.1]]

Hope that helps.

James Edward Gray II