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Re: Operator precedence [message #185063 is a reply to message #185043]

Tue, 25 February 2014 18:41

Christoph Michael Bec
Messages: 207
Registered: June 2013

Karma:

Senior Member

Thomas 'PointedEars' Lahn wrote:

> Christoph Michael Becker wrote:
>
>> Thomas 'PointedEars' Lahn wrote:
>>> Christoph Michael Becker wrote:
>>>> Thomas 'PointedEars' Lahn wrote:
>>>> > Ben Bacarisse wrote:
>>>> >> 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,
>>
>> ACK. :)
>>
>>> 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.
>>
>> I have to admit that this "definition" was far to inaccurate. However,
>> regarding the syntax alone it has some appeal.
>
> This “definition” is simply nonsense. An operator is not only an operator
> when it “can be used in arbitrary expressions”. In mathematics, from which
> is the definition that fits best here, an operator is a mapping from
> elements of one or more sets to elements of another or to the same set.

That sounds "very similar" to the definition of a function. ;)

> So
> *by definition* its context and its operands (members of said sets) matter.
>
>>>> >> 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;
>>
>> According to the C grammar[1], this use of the comma is not part of an
>> "exp", but rather an "init_declarator_list".
>>
>>> […] 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;
>>> ^
>>>
>>> However, in ECMAScript:
>>>
>>> | >>> var x = 42, 23;
>>
>> This use of the comma is not part of ECMAScript's "Expression", but
>> rather of "VariableDeclarationList".
>
> Please stop telling me things I know:

I have posted a message to Usenet. If you already knew these details,
fine. However, other readers might not.

Furthermore I was trying to stress my (resp. Ben's) point, that a comma
is not always an operator, even if a language defines a comma operator.

>>> | SyntaxError: Unexpected number
>>>
>>> What I meant instead was
>>>
>>> | >>> 42, 23
>>> | 23

--
Christoph M. Becker

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[Message index]

		Operator precedence By: Christoph Michael Bec on Sun, 23 February 2014 17:03
		Re: Operator precedence By: GS on Sun, 23 February 2014 19:42
		Re: Operator precedence By: Christoph Michael Bec on Sun, 23 February 2014 20:23
		Re: Operator precedence By: Jerry Stuckle on Sun, 23 February 2014 21:34
		Re: Operator precedence By: Richard Damon on Sun, 23 February 2014 23:36
		Re: Operator precedence By: Jerry Stuckle on Mon, 24 February 2014 02:09
		Re: Operator precedence By: Ben Bacarisse on Mon, 24 February 2014 04:49
		Re: Operator precedence By: Thomas 'PointedEars' on Mon, 24 February 2014 11:56
		Re: Operator precedence By: Christoph Michael Bec on Mon, 24 February 2014 16:38
		Re: Operator precedence By: Ben Bacarisse on Mon, 24 February 2014 21:25
		Re: Operator precedence By: Thomas 'PointedEars' on Mon, 24 February 2014 23:38
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 00:07
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 00:37
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 01:12
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 02:29
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 18:41
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 18:55
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 20:36
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 03:08
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 03:17
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 04:45
		Re: Operator precedence By: GS on Tue, 25 February 2014 21:45
		Re: Operator precedence By: Jerry Stuckle on Mon, 24 February 2014 12:00
		Re: Operator precedence By: Christoph Michael Bec on Mon, 24 February 2014 17:11
		Re: Operator precedence By: Jerry Stuckle on Mon, 24 February 2014 19:27
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 00:25
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 01:40
		Re: Operator precedence By: Ben Bacarisse on Mon, 24 February 2014 21:23
		Re: Operator precedence By: Jerry Stuckle on Mon, 24 February 2014 21:45
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 04:32
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 04:47
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 16:56
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 18:59
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 19:19
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 19:43
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 21:02
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 21:01
		Object constructors/destructors (was: Operator precedence) By: Christoph Michael Bec on Tue, 25 February 2014 21:19
		Re: Object constructors/destructors By: Jerry Stuckle on Tue, 25 February 2014 21:32
		Re: Object constructors/destructors By: Christoph Michael Bec on Tue, 25 February 2014 21:55
		Re: Object constructors/destructors By: Jerry Stuckle on Tue, 25 February 2014 22:01
		Re: Object constructors/destructors By: Adam Harvey on Tue, 25 February 2014 23:22
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 02:10
		Re: Object constructors/destructors By: Christoph Michael Bec on Wed, 26 February 2014 20:10
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 21:01
		Re: Object constructors/destructors By: Christoph Michael Bec on Wed, 26 February 2014 21:59
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 22:19
		Re: Object constructors/destructors By: Christoph Michael Bec on Wed, 26 February 2014 22:39
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 03:30
		Re: Object constructors/destructors By: Christoph Michael Bec on Thu, 27 February 2014 17:28
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 21:09
		Re: Object constructors/destructors By: Christoph Michael Bec on Fri, 28 February 2014 13:52
		Re: Object constructors/destructors By: Jerry Stuckle on Fri, 28 February 2014 14:08
		Re: Object constructors/destructors By: Christoph Michael Bec on Fri, 28 February 2014 15:52
		Re: Object constructors/destructors By: Jerry Stuckle on Fri, 28 February 2014 16:03
		Re: Object constructors/destructors By: Thomas 'PointedEars' on Thu, 27 February 2014 00:00
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 03:39
		Re: Object constructors/destructors By: Thomas 'PointedEars' on Thu, 27 February 2014 17:29
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 21:14
		Re: Object constructors/destructors By: Christoph Michael Bec on Tue, 25 February 2014 23:18
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 02:08
		Re: Object constructors/destructors By: Richard Damon on Wed, 26 February 2014 12:50
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 13:44
		Re: Object constructors/destructors By: Richard Damon on Thu, 27 February 2014 04:49
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 13:25
		Re: Object constructors/destructors By: Richard Damon on Sat, 01 March 2014 17:56
		Re: Object constructors/destructors By: Jerry Stuckle on Sat, 01 March 2014 19:22
		Re: Object constructors/destructors By: Richard Damon on Sun, 02 March 2014 19:28
		Re: Object constructors/destructors By: Jerry Stuckle on Sun, 02 March 2014 20:42
		Re: Object constructors/destructors By: Richard Damon on Sun, 02 March 2014 22:14
		Re: Object constructors/destructors By: Jerry Stuckle on Sun, 02 March 2014 22:48
		Re: Object constructors/destructors By: Tim Streater on Sun, 02 March 2014 23:05
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 21:08
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 21:29
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 23:15
		Re: Operator precedence By: Richard Damon on Tue, 25 February 2014 03:41
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 04:59
		Re: Operator precedence By: Richard Damon on Sat, 01 March 2014 18:39
		Re: Operator precedence By: Jerry Stuckle on Sat, 01 March 2014 19:29
		Re: Operator precedence By: Richard Damon on Sun, 02 March 2014 20:22
		Re: Operator precedence By: Jerry Stuckle on Sun, 02 March 2014 20:49
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 18:15
		Re: Operator precedence By: Ben Bacarisse on Sun, 23 February 2014 20:56
		Re: Operator precedence By: Christoph Michael Bec on Mon, 24 February 2014 13:28

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