From: Garthy D <garthy_lmkltybr@...>
Date: 2012-01-19T09:58:46+09:00
Subject: Elegant expression of sorting

Hi all,

I've found that for the current project I am working on that I am 
frequently doing sorts based on multiple keys. The comparisons on each 
key tend to vary, ie. sometimes I want descending rather than ascending, 
and other times the comparison itself is complex.

I usually do something like this:

foo.sort! {|a,b|
   # Ascending, primary.
   rv = a.key0 <=> b.key0
   # Descending, secondary.
   rv = b.key1 <=> a.key1 if rv == 0
   # A tricky and expensive comparison, tertiary.
   rv = a.magic(b) if rv == 0
   rv
}

Does anyone have any suggestions as to a more elegant way to express 
this? I'm after something that is logically equivalent, but easier to 
write and clearer to read.

Garth