From: Robert Klemme <bob.news@...>
Date: 2004-02-05T17:55:01+09:00
Subject: Re: RCR draft for enhanced "case..when..else..end" syntax


"Robert Klemme" <bob.news@gmx.net> schrieb im Newsbeitrag news:...
>
> "Sean O'Dell" <sean@celsoft.com> schrieb im Newsbeitrag
> news:200402041127.02778.sean@celsoft.com...
> > On Wednesday 04 February 2004 11:07 am, Guoliang Cao wrote:
> > > About my example, I don't think people should do a complex design.
> > > "if..elsif" is the answer in current Ruby capability.
> >
> > Personally, I like the idea of a more readable way to replace the
> if...elsif
> > paradigm.  It's a great idea!
>
> Hmm...  As someone else pointed out, if you are in excessive need of
such
> a construct, you should consider redesign.  Case constructs (or
> if...elsif...end cascades) are regarded to be not very OO IMHO.

Just to illustrate what I mean: in the case of the point coloring one
solve the problem with a mapping:

#!/usr/bin/ruby

Point = Struct.new( :x, :y )

class Point
  def range_x; x / 50; end
  def range_y; y / 50; end
end

colours = {
  [0, 0] => "white",
  [0, 1] => "white",
  [0, 2] => "white",
  [0, 3] => "white",
  [3, 0] => "white",
  [3, 1] => "white",
  [3, 2] => "white",
  [3, 3] => "white",

  [1, 0] => "blue",
  [2, 0] => "blue",

  [1, 1] => "grey",
  [1, 2] => "grey",
  [1, 3] => "grey",
}

colours.default= "black"

points = [
  Point.new( 0, 0 ),
  Point.new( 100, 0 ),
  Point.new( 55, 55 ),
  Point.new( 120, 210 ),
]

points.each do |point|
  p [point, colours[ [point.range_x, point.range_y] ] ]
end

IMHO this is also more efficient because the number of operations is
smaller than in a case / if...elsif...end cascade.  And it doesn't grow
linea with the number of colors involved.

Regards

    robert