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Groups > comp.lang.java.programmer > #35527
| From | Robert Klemme <shortcutter@googlemail.com> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Why not String compare? |
| Date | 2016-08-31 19:24 +0200 |
| Message-ID | <e2oi5kFbhheU1@mid.individual.net> (permalink) |
| References | (2 earlier) <1c9ad1a1-ee44-4a9f-a307-1dab14c4a921@googlegroups.com> <e2bo9iF9m4nU1@mid.individual.net> <d9d392a6-7361-4743-aaef-22ec3d126722@googlegroups.com> <e2nb40F26seU1@mid.individual.net> <slrnnsd9q3.456.avl@login.logic.tuwien.ac.at> |
On 31.08.2016 11:45, Andreas Leitgeb wrote: > Robert Klemme <shortcutter@googlemail.com> wrote: >> The implementor must ensure sgn(x.compareTo(y)) == -sgn(y.compareTo(x)) >> for all x and y. (This implies that x.compareTo(y) must throw an >> exception iff y.compareTo(x) throws an exception.) > > An equivalent "symmetry" could be expected from .equals, but isn't. Not necessarily since the underlying concept is different - equivalence relation vs. total order. You can reasonably say "that nothing is not equivalent to myself" while from "not equivalent" nothing follows for order. And btw. the concept of treating null special is quite common, for example with RDBMS. > It's not "symmetry" as such, that implied the requirement. It was > just pragmatically defined so for .compareTo while not for .equals. Well, but that is the contract. And I can see some sense in this. > Any usecase for including null into the natural ordering of certain > Comparable objects is just flawed. There, now you said it yourself. :-) Cheers robert -- remember.guy do |as, often| as.you_can - without end http://blog.rubybestpractices.com/
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Why not String compare? Eric Douglas <e.d.programmer@gmail.com> - 2016-08-26 09:00 -0700
Re: Why not String compare? Robert Klemme <shortcutter@googlemail.com> - 2016-08-26 18:49 +0200
Re: Why not String compare? Eric Douglas <e.d.programmer@gmail.com> - 2016-08-26 10:09 -0700
Re: Why not String compare? Robert Klemme <shortcutter@googlemail.com> - 2016-08-26 22:48 +0200
Re: Why not String compare? Eric Douglas <e.d.programmer@gmail.com> - 2016-08-26 13:55 -0700
Re: Why not String compare? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-26 17:29 -0400
Re: Why not String compare? Lew <lewbloch@gmail.com> - 2016-08-30 22:20 -0700
Re: Why not String compare? Robert Klemme <shortcutter@googlemail.com> - 2016-08-31 08:17 +0200
Re: Why not String compare? Andreas Leitgeb <avl@logic.at> - 2016-08-31 09:45 +0000
Re: Why not String compare? Robert Klemme <shortcutter@googlemail.com> - 2016-08-31 19:24 +0200
Re: Why not String compare? Andreas Leitgeb <avl@logic.at> - 2016-09-01 10:17 +0000
Re: Why not String compare? Robert Klemme <shortcutter@googlemail.com> - 2016-09-02 18:29 +0200
Re: Why not String compare? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-26 13:24 -0400
Re: Why not String compare? Eric Douglas <e.d.programmer@gmail.com> - 2016-08-26 10:48 -0700
Re: Why not String compare? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-26 14:50 -0400
Re: Why not String compare? Eric Douglas <e.d.programmer@gmail.com> - 2016-08-26 12:19 -0700
Re: Why not String compare? Lothar Kimmeringer <news200709@kimmeringer.de> - 2016-09-01 20:42 +0200
Re: Why not String compare? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-09-01 17:57 -0400
Re: Why not String compare? Eric Douglas <e.d.programmer@gmail.com> - 2016-08-26 11:03 -0700
Re: Why not String compare? Lothar Kimmeringer <news200709@kimmeringer.de> - 2016-09-02 21:54 +0200
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