Re: Comparisons and sorting of a numeric class....

From	Marko Rauhamaa <marko@pacujo.net>
Newsgroups	comp.lang.python
Subject	Re: Comparisons and sorting of a numeric class....
Date	2015-01-09 17:16 +0200
Organization	A noiseless patient Spider
Message-ID	<877fwwdlwh.fsf@elektro.pacujo.net> (permalink)
References	(9 earlier) <CALwzidkn5E3uxQ3Et9r-0_WUTjPLfHtY7mqwnhNVe2MGCi528Q@mail.gmail.com> <mailman.17483.1420742711.18130.python-list@python.org> <54afc949$0$12985$c3e8da3$5496439d@news.astraweb.com> <mailman.17524.1420807429.18130.python-list@python.org> <87lhlcro2s.fsf@jester.gateway.sonic.net>

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Paul Rubin <no.email@nospam.invalid>:

> Marko's suggestion
>
>     rv = f()
>     if rv is not None:
>         return rv
>     rv = g()
>     if rv is not None:
>         return rv
>     return h()
>
> seems unspeakably ugly.

Well, "unspeakably" is exaggeration IMO. It is a bit lengthy but it is
crystal clear. While the "or" pattern is neat, I wouldn't make too much
of it.

> Rather than None on failure maybe f() and g() could return an empty
> list on failure, or a one-element list containing the item on success.
> That uses lists to simulate a Maybe type.
>
> Then the above could go (Python 3, untested):
>
>   def tries():
>     yield from f()
>     yield from g()
>     yield [h()]
>   return tries().next()

I think the medicine in this case is worse than the disease.


Marko

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Re: Comparisons and sorting of a numeric class.... Andrew Robinson <andrew3@r3dsolutions.com> - 2015-01-06 18:01 -0800
  Re: Comparisons and sorting of a numeric class.... Steven D'Aprano <steve@pearwood.info> - 2015-01-07 08:10 +0000
    Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-07 19:21 +1100
    Re: Comparisons and sorting of a numeric class.... Marko Rauhamaa <marko@pacujo.net> - 2015-01-07 12:01 +0200
      Re: Comparisons and sorting of a numeric class.... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-08 10:46 +1100
        Re: Comparisons and sorting of a numeric class.... Marko Rauhamaa <marko@pacujo.net> - 2015-01-08 08:21 +0200
          Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-08 07:57 -0700
            Re: Comparisons and sorting of a numeric class.... Marko Rauhamaa <marko@pacujo.net> - 2015-01-08 21:41 +0200
          Re: Comparisons and sorting of a numeric class.... Chris Kaynor <ckaynor@zindagigames.com> - 2015-01-08 10:44 -0800
            Re: Comparisons and sorting of a numeric class.... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-09 23:27 +1100
              Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-09 23:43 +1100
                Re: Comparisons and sorting of a numeric class.... Marko Rauhamaa <marko@pacujo.net> - 2015-01-09 16:28 +0200
                Re: Comparisons and sorting of a numeric class.... Paul Rubin <no.email@nospam.invalid> - 2015-01-09 07:06 -0800
                Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-10 02:14 +1100
                Re: Comparisons and sorting of a numeric class.... Marko Rauhamaa <marko@pacujo.net> - 2015-01-09 17:16 +0200

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