From: Dave Thomas <Dave@...>
Date: 2001-05-17T09:12:41+09:00
Subject: [ruby-talk:15320] Re: Pluggable sorting - How would you do it?

Wayne Scott <wscott@bitmover.com> writes:

> From: matz@zetabits.com (Yukihiro Matsumoto)
> > It implements Schwartzian transformation inside.  I like this idea,
> > but am not yet sure "sort_by" is a proper name for the behavior.
> 
> How about "sort_using" ??
> 
> BTW I have noticed that sorting on multiple fields feels clumsy in
> Ruby.
> 
> tbl.sort! do |a,b| 
>     r = b[0] <=> a[0]
>     r = a[1] <=> b[1] unless r.nonzero?
>     r
> end
> 
> vs
> 
> sort {$b->[0] <=> $a->[0]
> 	       ||
>       $a->[1] <=> $b->[1]} @tbl;  
> 
> in perl.

The example in http://www.rubycentral.com/book/ref_c_numeric.html#nonzero_qm
shows a slightly more idiomatic form:

  tbl.sort {|a,b| (b[0] <=> a[0].nonzero? || b[1] <=> a[1] }

This turns out to be exactly the same number of characters as the Perl
version (give or take :)

Of course, if tbl consists of 2 element arrays, you could also just
write

   tbl.sort.reverse

as Array#<=> does what you'd expect.


Regards


Dave