From: Ross Bamford <rossrt@...>
Date: 2006-02-07T23:12:11+09:00
Subject: Re: Feeling sharp?  Sort an array subset in place.

On Tue, 2006-02-07 at 17:28 +0900, Michael Judge wrote:
> Here's the situation: I have an array and I'd like to sort certain
> elements in place -- without touching the others.

I agree with Robert that you should probably think about why your data
is kept this way. But here's one I've used:

	class Array
	  def select_sort!(sort_proc = nil)
	    t = []
	    map! { |x| if yield x then t << x; nil else x end }
	    t.sort!(&sort_proc)
	    map! { |x| x or t.shift }
	  end
	end

Which works like:

a = [2,'a',3,'b','c',1]
>> # => [2, "a", 3, "b", "c", 1]
a.select_sort! { |x| x.is_a? Fixnum }
>> p a
# => [1, "a", 2, "b", "c", 3]
a.select_sort!(lambda { |x,y| y <=> x }) { |x| x.is_a? Fixnum }
>> p a
# => [3, "a", 2, "b", "c", 1]

But it breaks down if your array contains nil elements beforehand, and
has that nasty two-block look about it.

-- 
Ross Bamford - rosco@roscopeco.REMOVE.co.uk