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Groups > comp.lang.php > #12936
| Message-ID | <1996520.IoEltsQCmd@PointedEars.de> (permalink) |
|---|---|
| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
| Organization | PointedEars Software (PES) |
| Date | 2014-02-25 01:37 +0100 |
| Subject | Re: Operator precedence |
| Newsgroups | comp.lang.php |
| References | (5 earlier) <0.914eafe42061d70d7566.20140224044930GMT.87fvn9ru79.fsf@bsb.me.uk> <4293011.KJL4Tygh8x@PointedEars.de> <0.60537d4b87ccab3ac30a.20140224212551GMT.87ppmcqk2o.fsf@bsb.me.uk> <6171065.55Kx8BzDJ9@PointedEars.de> <530bdeb5$0$9519$9b4e6d93@newsspool1.arcor-online.net> |
Christoph Michael Becker wrote:
> Thomas 'PointedEars' Lahn wrote:
>> Ben Bacarisse wrote:
>>> Thomas 'PointedEars' Lahn <PointedEars@web.de> writes:
>>>> Ben Bacarisse wrote:
>>>>> […] Expressions are built from operators, but is ',' an operator in
>>>>> [PHP?
>>>>> It appears in the operator precedence table but it isn't an operator
>>>>> in an sense that would normally be understood by someone familiar with
>>>>> these terms.
>>>>
>>>> ECMAScript has a “Comma Operator”, too.
>>>
>>> But my point was the PHP doesn't have one --
>>
>> But it does:
>>
>> for ($i = 0, $j = 42; $i < $j; ++$i);
>> ^
>
> The comma is used in sevaral places in the PHP grammar[1]. However,
> IMHO your example (inside a for_expr) is the only case where the comma
> is used as an operator. The other uses are for declaration and
> parameter lists (spoken in a broad sense).
I am aware of that.
>>> not in any normal sense of the word.
>>
>> Please define what you consider to be an operator in a “normal sense of
>> the word”.
>
> It might be defined as an operator that can be used in arbitrary
> expressions.
A speculation, one that is almost self-evidently false. Just consider the
operators (including, but not just in, programming languages) that require
their operands to be of a certain type.
> Consider the following ECMAScript expression:
>
> a = 1, b = 2;
>
> The "equivalent" expression in PHP is a syntax error:
>
> $a = 1, $b = 2;
I am aware of that.
>>> ECMAScript really does have one (like C and C++ do).
>>
>> Why do you think C and C++ have a comma operator (like ECMAScript)?
>
> According to the C grammar[2]:
>
> exp : assignment_exp
> | exp ',' assignment_exp
>
> [1] <http://lxr.php.net/xref/PHP_5_5/Zend/zend_language_parser.y>
> [2] <http://www.cs.man.ac.uk/~pjj/bnf/c_syntax.bnf>
ACK; I stand corrected. For reasons I cannot explain (probably it is just
late), I had assumed that the comma operator in ECMAScript also worked with
assignments, and this is what I tested with C and C++:
$ cat foo.c
#include <stdio.h>
int main() {
int x = 42, 23;
printf("%i\n", x);
return 0;
}
$ gcc -Wall -o foo.out foo.c
foo.c: In function ‘main’:
foo.c:4:15: error: expected identifier or ‘(’ before numeric constant
int x = 42, 23;
^
$ cat foo.cpp
#include <iostream>
using namespace std;
int main() {
int x = 42, 23;
cout << x << endl;
return 0;
}
$ g++ -Wall -o foo.out foo.cpp 2>&1| tee /tmp/v6wTKDF/0
foo.cpp: In function ‘int main()’:
foo.cpp:5:15: error: expected unqualified-id before numeric constant
int x = 42, 23;
^
However, in ECMAScript:
| >>> var x = 42, 23;
| SyntaxError: Unexpected number
What I meant instead was
| >>> 42, 23
| 23
which does work like that in certain contexts in C and C++, but not in PHP:
$ cat foo.c
#include <stdio.h>
int main() {
printf("%i\n", (42, 23));
return 0;
}
$ gcc -Wall -o foo.out foo.c 2>&1| tee /tmp/vJ0RqVR/0
foo.c: In function ‘main’:
foo.c:4:21: warning: left-hand operand of comma expression has no effect
[-Wunused-value]
printf("%i\n", (42, 23));
^
$ ./foo.out
23
$ cat foo.cpp
#include <iostream>
using namespace std;
int main() {
cout << (42, 23) << endl;
return 0;
}
$ g++ -Wall -o foo.out foo.cpp
foo.cpp: In function ‘int main()’:
foo.cpp:5:16: warning: left operand of comma operator has no effect
[-Wunused-value]
cout << (42, 23) << endl;
^
$ ./foo.out
23
$ php -r 'echo (42, 23) . "\n";'
PHP Parse error: syntax error, unexpected ',' in Command line code on line
1
[Interesting that gcc says “operand” and “comma *expression*”, while g++
says “operand” and “comma *operator*”.]
PointedEars
--
Sometimes, what you learn is wrong. If those wrong ideas are close to the
root of the knowledge tree you build on a particular subject, pruning the
bad branches can sometimes cause the whole tree to collapse.
-- Mike Duffy in cljs, <news:Xns9FB6521286DB8invalidcom@94.75.214.39>
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Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-23 18:03 +0100
Re: Operator precedence GS <nomail@nospam.org.invalid> - 2014-02-23 19:42 +0000
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-23 21:23 +0100
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-23 16:34 -0500
Re: Operator precedence Richard Damon <Richard@Damon-Family.org> - 2014-02-23 18:36 -0500
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-23 21:09 -0500
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-24 04:49 +0000
Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-24 12:56 +0100
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-24 17:38 +0100
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-24 21:25 +0000
Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 00:38 +0100
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 01:07 +0100
Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 01:37 +0100
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 02:12 +0100
Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 03:29 +0100
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 19:41 +0100
Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 19:55 +0100
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 21:36 +0100
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 03:08 +0000
Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 04:17 +0100
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 04:45 +0000
Re: Operator precedence GS <nomail@nospam.org.invalid> - 2014-02-25 21:45 +0000
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 07:00 -0500
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-24 18:11 +0100
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 14:27 -0500
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 01:25 +0100
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 20:40 -0500
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-24 21:23 +0000
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 16:45 -0500
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 04:32 +0000
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 23:47 -0500
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 16:56 +0000
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 13:59 -0500
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 20:19 +0100
Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 20:43 +0100
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 16:02 -0500
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 16:01 -0500
Object constructors/destructors (was: Operator precedence) Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 22:19 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 16:32 -0500
Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 22:55 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 17:01 -0500
Re: Object constructors/destructors Adam Harvey <usenet@adamharvey.name> - 2014-02-25 23:22 +0000
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 21:10 -0500
Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-26 21:10 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 16:01 -0500
Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-26 22:59 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 17:19 -0500
Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-26 23:39 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 22:30 -0500
Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-27 18:28 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-27 16:09 -0500
Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-28 14:52 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-28 09:08 -0500
Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-28 16:52 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-28 11:03 -0500
Re: Object constructors/destructors Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-27 01:00 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 22:39 -0500
Re: Object constructors/destructors Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-27 18:29 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-27 16:14 -0500
Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-26 00:18 +0100
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 21:08 -0500
Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-02-26 07:50 -0500
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 08:44 -0500
Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-02-26 23:49 -0500
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-27 08:25 -0500
Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-03-01 12:56 -0500
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-01 14:22 -0500
Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-03-02 14:28 -0500
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-02 15:42 -0500
Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-03-02 17:14 -0500
Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-02 17:48 -0500
Re: Object constructors/destructors Tim Streater <timstreater@greenbee.net> - 2014-03-02 23:05 +0000
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 21:08 +0000
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 22:29 +0100
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 23:15 +0000
Re: Operator precedence Richard Damon <Richard@Damon-Family.org> - 2014-02-24 22:41 -0500
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 23:59 -0500
Re: Operator precedence Richard Damon <Richard@Damon-Family.org> - 2014-03-01 13:39 -0500
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-01 14:29 -0500
Re: Operator precedence Richard Damon <Richard@Damon-Family.org> - 2014-03-02 15:22 -0500
Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-02 15:49 -0500
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 19:15 +0100
Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-23 20:56 +0000
Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-24 14:28 +0100
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