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Re: Hash Surprises with Fixnum, #hash, and #eql?

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Phillip Gawlowski wrote in post #991471:
>> If you see inheritance as "is a" relationship then inheritance would
>> be Rational < Real < Complex but not the other way round. Otherwise
>> you cannot use a subclass instance everywhere you were using a
>> superclass instance.
>
> Though, does the "is a" relationship hold up? I think it's more of a
> "kind of" relationship, where subsequent classes are defined in ever
> more detail (so, you'd inherit Floats from Integers, and Complex from
> Float).

Isn't this the old "ellipse is_a circle, or vice versa" debate?

If you make Circle the top class, then Ellipse reimplements pretty much 
everything (draw, area, etc); there's no useful code sharing. If you 
make Ellipse the top class, then Circle is just a special constrained 
case of Ellipse.

Translating to the current discussion, substitute Float for Circle and 
Ellipse for Complex.

Ruby's answer is: neither is a subclass of the other. Both inherit from 
Numeric. That is, Circle and Ellipse are both a Shape. Or in other 
words, "who cares"?

Eventually you come to realise that a lot of what is taught in object 
oriented classes and textbooks is tosh :-)

-- 
Posted via http://www.ruby-forum.com/.

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Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-07 14:01 +1000
  Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-07 04:19 -0500
    Re: Hash Surprises with Fixnum, #hash, and #eql? Phillip Gawlowski <cmdjackryan@googlemail.com> - 2011-04-07 06:20 -0500
      Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-07 06:53 -0500
        Re: Hash Surprises with Fixnum, #hash, and #eql? Phillip Gawlowski <cmdjackryan@googlemail.com> - 2011-04-07 08:21 -0500
          Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-07 08:43 -0500
            Re: Hash Surprises with Fixnum, #hash, and #eql? Phillip Gawlowski <cmdjackryan@googlemail.com> - 2011-04-07 09:02 -0500
              Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-07 09:28 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Phillip Gawlowski <cmdjackryan@googlemail.com> - 2011-04-07 09:49 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-07 10:11 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Phillip Gawlowski <cmdjackryan@googlemail.com> - 2011-04-07 10:31 -0500
              Re: Hash Surprises with Fixnum, #hash, and #eql? Brian Candler <b.candler@pobox.com> - 2011-04-07 11:06 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Vincent Manis <vmanis@telus.net> - 2011-04-07 17:42 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-08 01:55 -0500
    Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-08 17:29 +1000
      Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-08 05:12 -0500
        Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-09 11:21 +1000
          Re: Hash Surprises with Fixnum, #hash, and #eql? Charles Oliver Nutter <headius@headius.com> - 2011-04-10 19:02 -0500
            Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-11 13:17 +1000
              Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-12 04:09 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-13 12:02 +1000
                Re: Hash Surprises with Fixnum, #hash, and #eql? Charles Oliver Nutter <headius@headius.com> - 2011-04-13 00:51 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-13 16:32 +1000
                Re: Hash Surprises with Fixnum, #hash, and #eql? Charles Oliver Nutter <headius@headius.com> - 2011-04-13 07:23 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-14 07:38 +1000
                Re: Hash Surprises with Fixnum, #hash, and #eql? Charles Oliver Nutter <headius@headius.com> - 2011-04-14 00:36 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-14 15:55 +1000
                Re: Hash Surprises with Fixnum, #hash, and #eql? Charles Oliver Nutter <headius@headius.com> - 2011-04-19 17:41 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-21 12:49 +1000
                Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-21 06:28 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-21 22:32 +1000
                Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-21 08:51 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? John W Higgins <wishdev@gmail.com> - 2011-04-21 11:11 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Charles Oliver Nutter <headius@headius.com> - 2011-04-27 00:33 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-27 01:44 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Charles Oliver Nutter <headius@headius.com> - 2011-04-27 16:22 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Charles Oliver Nutter <headius@headius.com> - 2011-04-27 00:23 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-30 17:43 +1000
                Re: Hash Surprises with Fixnum, #hash, and #eql? Charles Oliver Nutter <headius@headius.com> - 2011-05-01 23:01 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Robert Klemme <shortcutter@googlemail.com> - 2011-04-13 02:08 -0500
                Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-14 07:36 +1000
      Re: Hash Surprises with Fixnum, #hash, and #eql? Xavier Noria <fxn@hashref.com> - 2011-04-08 19:00 -0500
        Re: Hash Surprises with Fixnum, #hash, and #eql? Clifford Heath <no@spam.please.net> - 2011-04-09 11:22 +1000
  Re: Hash Surprises with Fixnum, #hash, and #eql? Mazi Ayışığı <mazi.ayisigi@gmail.com> - 2011-04-07 17:16 -0700

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