From: Daniel Carrera <dcarrera@...>
Date: 2003-01-12T22:09:09+09:00
Subject: Re: sorting with the Swartzian transform

Ruby never ceases to amaze me.  :)

I still think it's good to understand Swartzian transforms because
Enumerable#sort_by won't help in the general case when you can't easily
assign a number to ech object.

Still, it's very cool to have that in the language.

Daniel Carrera
Graduate Teaching Assistant.  Math Dept.
University of Maryland.  (301) 405-5137

On Sun, 12 Jan 2003, WATANABE Hirofumi wrote:

> Hi,
>
> Daniel Carrera <dcarrera@math.umd.edu> writes:
>
> > This email is simply for the benefit and/or reading pleasure of ruby
> > hackers.  In particular those without a strong Perl background.  I just
> > had to do a Swartzian transform in Ruby and it occurred to me that someone
> > might benefit from my experience.
>
> Ruby 1.8 has Enumerable#sort_by.
> This method is equivalent to:
>
>   module Enumerable
>     def sort_by
>       ary = map { |i| [yield(i), i] }
>       ary.sort! { |a, b| a[0] <=> b[0] }
>       ary.map! { |i| i[1] }
>     end
>   end
>
> --
> eban
>
>