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| From | Ben Pfaff <blp@cs.stanford.edu> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Precedence Misunderstanding |
| Date | 2012-07-16 21:54 -0700 |
| Message-ID | <874np7j8br.fsf@blp.benpfaff.org> (permalink) |
| References | <ju2p36$qj9$1@dont-email.me> |
Charles Richmond <frizzle@aquaporin4.com> writes: > Can someone explain how "&&" can have a *higher* precedence than > "||"... when the series of AND's and OR's are just going to be done > left to right??? I think there's a lot of confusion on this point because we aren't taught about this in our math classes. That's because side effects don't exist in math, so order of evaluation doesn't matter. Precedence does, but that's a different issue. Consider 2 * 3 + 4 * 5. Precedence says that this must be treated the same as (2 * 3) + (4 * 5). But once you figure that out, you have a choice: you can evaluate 2 * 3 first or you can evaluate 4 * 5 first, because the order doesn't matter. No one bothers to say that you have to evaluate left-to-right or even that you have to evaluate right-to-left, because that would not change the eventual result in any way. When side effects come in, the situation changes. a() + b() might do something completely different depending on which of a() or b() you call first. Extending it to a() + b() * c(), then precedence comes in. C doesn't say in what order a(), b(), and c() are evaluated, but it does say that once they are evaluated, you have to multiply b() by c(), not by a(). I hope that helps.
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Precedence Misunderstanding Charles Richmond <frizzle@aquaporin4.com> - 2012-07-16 23:18 -0500
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-16 21:54 -0700
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-16 22:13 -0700
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-16 22:36 -0700
Re: Precedence Misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-17 13:57 +0100
Re: Precedence Misunderstanding "Charles Richmond" <numerist@aquaporin4.com> - 2012-07-17 13:35 -0500
Re: Precedence Misunderstanding "io_x" <a@b.c.invalid> - 2012-07-17 20:48 +0200
Re: Precedence Misunderstanding Robert Wessel <robertwessel2@yahoo.com> - 2012-07-17 13:45 -0500
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-17 12:27 -0700
Re: Precedence Misunderstanding Willem <willem@toad.stack.nl> - 2012-07-17 20:20 +0000
Re: Precedence Misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-17 20:34 +0100
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-17 12:39 -0700
Re: Precedence Misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-17 20:57 +0100
Re: Precedence Misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-17 20:48 +0100
Re: Precedence Misunderstanding Philip Lantz <prl@canterey.us> - 2012-07-17 21:12 -0700
Re: Precedence Misunderstanding Ike Naar <ike@iceland.freeshell.org> - 2012-07-18 07:14 +0000
Re: Precedence Misunderstanding "BartC" <bc@freeuk.com> - 2012-07-18 10:11 +0100
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-18 09:18 -0700
Re: Precedence Misunderstanding Rui Maciel <rui.maciel@gmail.com> - 2012-07-18 18:10 +0100
Re: Precedence Misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-18 18:27 +0100
Re: Precedence Misunderstanding Rui Maciel <rui.maciel@gmail.com> - 2012-07-18 18:53 +0100
Re: Precedence Misunderstanding Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-18 21:07 +0100
Re: Precedence Misunderstanding Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-07-19 20:47 +0300
Re: Precedence Misunderstanding Philip Lantz <prl@canterey.us> - 2012-07-18 23:54 -0700
Re: Precedence Misunderstanding Ike Naar <ike@sverige.freeshell.org> - 2012-07-19 07:21 +0000
Re: Precedence Misunderstanding "BartC" <bc@freeuk.com> - 2012-07-17 20:42 +0100
Re: Precedence Misunderstanding Willem <willem@toad.stack.nl> - 2012-07-17 20:38 +0000
Re: Precedence Misunderstanding Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-07-19 20:54 +0300
Re: Precedence Misunderstanding Willem <willem@toad.stack.nl> - 2012-07-19 22:02 +0000
Re: Precedence Misunderstanding pete <pfiland@mindspring.com> - 2012-07-17 22:31 -0400
Re: Precedence Misunderstanding Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-07-18 00:35 -0700
Re: Precedence Misunderstanding Rui Maciel <rui.maciel@gmail.com> - 2012-07-17 22:16 +0100
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-17 14:22 -0700
Re: Precedence Misunderstanding Rui Maciel <rui.maciel@gmail.com> - 2012-07-18 16:35 +0100
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-18 10:03 -0700
Re: Precedence Misunderstanding Rui Maciel <rui.maciel@gmail.com> - 2012-07-18 18:32 +0100
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-18 10:45 -0700
Re: Precedence Misunderstanding Rui Maciel <rui.maciel@gmail.com> - 2012-07-18 19:29 +0100
Re: Precedence Misunderstanding Ben Pfaff <blp@cs.stanford.edu> - 2012-07-18 11:45 -0700
Re: Precedence Misunderstanding Keith Thompson <kst-u@mib.org> - 2012-07-18 13:26 -0700
Re: Precedence Misunderstanding Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-07-19 00:51 -0700
Re: Precedence Misunderstanding Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-07-19 00:11 -0700
Re: Precedence Misunderstanding Robert Wessel <robertwessel2@yahoo.com> - 2012-07-17 00:05 -0500
Re: Precedence Misunderstanding Ike Naar <ike@iceland.freeshell.org> - 2012-07-17 07:40 +0000
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