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Re: bug in is_numeric [message #181330 is a reply to message #181328]

Sun, 12 May 2013 17:38

Thomas 'PointedEars'
Messages: 701
Registered: October 2010

Karma:

Senior Member

Thomas Mlynarczyk wrote:

> Sanders Kaufman schrieb:
>>> if(is_numeric('x11.11c') returns TRUE
>> Try it without the quotation marks around the number.
>
> Which number? x11.11c is not a number.

The misconception might partially draw from the fact that 0x11 is a number,
the hexadecimal representation of decimal 16¹ + 16⁰ = 17 (even in PHP). In
other programming languages that require a leading “0” and do not have “.”
as (concatenation) operator,

x11.11c

could be the representation of decimal 16¹ + 16⁰ + 16⁻¹ + 16⁻² + 13 × 16⁻³ =
17.06958 (BTW, I have written a drop-in replacement for ECMAScript's
parseFloat() that can do that, with the usual rounding errors [1]).

In PHP, however,

x11.11c

would be equivalent to

(x11) . (11c)

which is a syntax error because constant identifiers must not start with a
decimal digit, and decimal literals must not contain a letter:

$ php -r 'echo x11 . 11c;'
PHP Parse error: syntax error, unexpected 'c' (T_STRING), expecting ',' or
';' in Command line code on line 1

$ php -r 'echo x11 . 11;'
PHP Notice: Use of undefined constant x11 - assumed 'x11' in Command line
code on line 1
PHP Stack trace:
PHP 1. {main}() Command line code:0
x1111

$ php -r 'echo x11 . x11c;'
PHP Notice: Use of undefined constant x11 - assumed 'x11' in Command line
code on line 1
PHP Stack trace:
PHP 1. {main}() Command line code:0
PHP Notice: Use of undefined constant x11c - assumed 'x11c' in Command line
code on line 1
PHP Stack trace:
PHP 1. {main}() Command line code:0
x11x11c

$ php -v
PHP 5.4.4-15 (cli) (built: Mar 22 2013 15:41:03)
Copyright (c) 1997-2012 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2012 Zend Technologies
with XCache v3.0.1, Copyright (c) 2005-2013, by mOo
with Xdebug v2.2.1, Copyright (c) 2002-2012, by Derick Rethans
with XCache Optimizer v3.0.1, Copyright (c) 2005-2013, by mOo
with XCache Cacher v3.0.1, Copyright (c) 2005-2013, by mOo
with XCache Coverager v3.0.1, Copyright (c) 2005-2013, by mOo

>> Quotes turn a number into a string.
>
> is_numeric() should return TRUE if the argument is a string containing
> the representation of a numeric value. That's the point of this function.

Not quite. It also works for non-strings as arguments. [2]

is_numeric(1) === TRUE

Thus it is better to say that is_numeric() returns TRUE if PHP's ”type
juggling” [3] (or, more formal, “implicit type conversion”), if necessary,
would allow the argument to be interpreted as a numeric value in an
arithmetic expression.

_____
[1] <http://pointedears.de/scripts/test/string>
[2] <http://php.net/is_numeric>
[3] <http://php.net/manual/en/language.types.type-juggling.php>

PointedEars
--
> If you get a bunch of authors […] that state the same "best practices"
> in any programming language, then you can bet who is wrong or right...
Not with javascript. Nonsense propagates like wildfire in this field.
-- Richard Cornford, comp.lang.javascript, 2011-11-14

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[Message index]

		bug in is_numeric By: fred on Sun, 12 May 2013 14:22
		Re: bug in is_numeric By: Salvatore on Sun, 12 May 2013 15:31
		Re: bug in is_numeric By: Luuk on Sun, 12 May 2013 15:55
		Re: bug in is_numeric By: Luuk on Sun, 12 May 2013 15:58
		Re: bug in is_numeric By: Thomas Mlynarczyk on Sun, 12 May 2013 16:06
		Re: bug in is_numeric By: Denis McMahon on Sun, 12 May 2013 16:24
		Re: bug in is_numeric By: fred on Sun, 12 May 2013 17:41
		Re: bug in is_numeric By: Erwin Moller on Mon, 13 May 2013 11:50
		Re: bug in is_numeric By: fred on Mon, 13 May 2013 13:58
		Re: bug in is_numeric By: Jerry Stuckle on Mon, 13 May 2013 14:11
		Re: bug in is_numeric By: fred on Mon, 13 May 2013 14:15
		Re: bug in is_numeric By: Erwin Moller on Mon, 13 May 2013 15:29
		Re: bug in is_numeric By: J.O. Aho on Mon, 13 May 2013 17:55
		Re: bug in is_numeric By: Richard Yates on Tue, 14 May 2013 13:41
		Re: bug in is_numeric By: SwissCheese on Wed, 15 May 2013 01:43
		Re: bug in is_numeric By: Jerry Stuckle on Wed, 15 May 2013 03:01
		Re: bug in is_numeric By: SwissCheese on Wed, 15 May 2013 09:48
		Re: bug in is_numeric By: Jerry Stuckle on Wed, 15 May 2013 10:11
		Re: bug in is_numeric By: SwissCheese on Thu, 16 May 2013 22:36
		Re: bug in is_numeric By: Thomas 'PointedEars' on Wed, 15 May 2013 13:19
		Re: bug in is_numeric By: Christoph Becker on Wed, 15 May 2013 18:23
		Re: bug in is_numeric By: Thomas 'PointedEars' on Wed, 15 May 2013 18:49
		Re: bug in is_numeric By: Christoph Becker on Wed, 15 May 2013 19:58
		Re: bug in is_numeric By: Thomas 'PointedEars' on Wed, 15 May 2013 20:20
		Re: bug in is_numeric By: Christoph Becker on Wed, 15 May 2013 20:42
		Re: bug in is_numeric By: Thomas Mlynarczyk on Wed, 15 May 2013 21:53
		Re: bug in is_numeric By: Christoph Becker on Wed, 15 May 2013 22:29
		Re: bug in is_numeric By: Christoph Becker on Wed, 15 May 2013 22:40
		Re: bug in is_numeric By: Thomas 'PointedEars' on Thu, 16 May 2013 03:00
		Re: bug in is_numeric By: SwissCheese on Thu, 16 May 2013 22:16
		Re: bug in is_numeric By: Thomas 'PointedEars' on Thu, 16 May 2013 22:45
		Re: bug in is_numeric By: SwissCheese on Fri, 17 May 2013 02:52
		Re: bug in is_numeric By: Thomas 'PointedEars' on Fri, 17 May 2013 16:33
		Re: bug in is_numeric By: Christoph Becker on Fri, 17 May 2013 18:39
		Re: bug in is_numeric By: Thomas 'PointedEars' on Fri, 17 May 2013 21:45
		Re: bug in is_numeric By: Christoph Becker on Sat, 18 May 2013 12:47
		Re: bug in is_numeric By: SwissCheese on Thu, 16 May 2013 00:57
		Re: bug in is_numeric By: Jerry Stuckle on Thu, 16 May 2013 04:09
		Re: bug in is_numeric By: Christoph Becker on Thu, 16 May 2013 23:17
		Re: bug in is_numeric By: Jerry Stuckle on Fri, 17 May 2013 00:30
		Re: bug in is_numeric By: Christoph Becker on Sat, 18 May 2013 12:51
		Re: bug in is_numeric By: Jerry Stuckle on Sat, 18 May 2013 14:07
		Re: bug in is_numeric By: Sanders Kaufman on Sat, 18 May 2013 16:56
		Re: bug in is_numeric By: Jerry Stuckle on Sat, 18 May 2013 18:32
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sat, 18 May 2013 20:24
		Re: bug in is_numeric By: Jerry Stuckle on Sat, 18 May 2013 21:01
		Re: bug in is_numeric By: Denis McMahon on Sat, 18 May 2013 21:58
		Re: bug in is_numeric By: Jerry Stuckle on Sat, 18 May 2013 23:21
		Re: bug in is_numeric By: Denis McMahon on Sun, 19 May 2013 02:22
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 19 May 2013 02:41
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 10:28
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 19 May 2013 13:42
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 16:42
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 19 May 2013 18:39
		Re: bug in is_numeric By: Sanders Kaufman on Tue, 21 May 2013 06:01
		Re: bug in is_numeric By: Jerry Stuckle on Tue, 21 May 2013 09:59
		Re: bug in is_numeric By: The Natural Philosoph on Sun, 19 May 2013 06:49
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 10:31
		Re: bug in is_numeric By: The Natural Philosoph on Sun, 19 May 2013 11:39
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 19 May 2013 13:43
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 16:52
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 19 May 2013 18:42
		Re: bug in is_numeric By: Sanders Kaufman on Tue, 21 May 2013 06:03
		Re: bug in is_numeric By: Jerry Stuckle on Tue, 21 May 2013 10:00
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 16:45
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 10:27
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 19 May 2013 13:45
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 16:37
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 19 May 2013 18:43
		Re: bug in is_numeric By: Sanders Kaufman on Tue, 21 May 2013 05:59
		Re: bug in is_numeric By: Jerry Stuckle on Tue, 21 May 2013 10:02
		Re: bug in is_numeric By: Sanders Kaufman on Sat, 18 May 2013 22:08
		Re: bug in is_numeric By: The Natural Philosoph on Sat, 18 May 2013 22:58
		Re: bug in is_numeric By: Jerry Stuckle on Sat, 18 May 2013 23:22
		Re: bug in is_numeric By: Sanders Kaufman on Sat, 18 May 2013 22:11
		Re: bug in is_numeric By: Jerry Stuckle on Sat, 18 May 2013 23:23
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 10:35
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 19 May 2013 13:46
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 16:23
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 19 May 2013 18:44
		Re: bug in is_numeric By: Sanders Kaufman on Tue, 21 May 2013 05:54
		Re: bug in is_numeric By: Jerry Stuckle on Tue, 21 May 2013 10:03
		Re: bug in is_numeric By: fred on Thu, 23 May 2013 14:38
		Re: bug in is_numeric By: Arno Welzel on Sat, 01 June 2013 15:36
		Re: bug in is_numeric By: Jerry Stuckle on Sat, 01 June 2013 18:54
		Re: bug in is_numeric By: Arno Welzel on Wed, 05 June 2013 13:25
		Re: bug in is_numeric By: Jerry Stuckle on Wed, 05 June 2013 14:34
		Re: bug in is_numeric By: Arno Welzel on Wed, 05 June 2013 15:02
		Re: bug in is_numeric By: Jerry Stuckle on Wed, 05 June 2013 16:30
		OT: What you say is not always what you mean (was: Re: bug in is_numeric) By: Arno Welzel on Wed, 05 June 2013 18:20
		Re: OT: What you say is not always what you mean By: Jerry Stuckle on Wed, 05 June 2013 18:40
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sat, 18 May 2013 19:51
		Re: bug in is_numeric By: Sanders Kaufman on Sat, 18 May 2013 22:13
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sat, 18 May 2013 22:49
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 10:24
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sun, 19 May 2013 10:40
		Re: bug in is_numeric By: The Natural Philosoph on Sun, 19 May 2013 11:43
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 19 May 2013 16:29
		Re: bug in is_numeric By: Norman Peelman on Sat, 18 May 2013 18:53
		Re: bug in is_numeric By: SwissCheese on Thu, 16 May 2013 22:41
		Re: bug in is_numeric By: Daniel Pitts on Mon, 13 May 2013 15:35
		Re: bug in is_numeric By: Denis McMahon on Mon, 13 May 2013 20:26
		Re: bug in is_numeric By: Denis McMahon on Mon, 13 May 2013 20:15
		Re: bug in is_numeric By: Robert Heller on Sun, 12 May 2013 18:03
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sun, 12 May 2013 16:03
		Re: bug in is_numeric By: fred on Sun, 12 May 2013 17:34
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sun, 12 May 2013 17:40
		Re: bug in is_numeric By: Luuk on Sun, 12 May 2013 19:51
		Re: bug in is_numeric By: Sanders Kaufman on Sun, 12 May 2013 16:47
		Re: bug in is_numeric By: Luuk on Sun, 12 May 2013 16:56
		Re: bug in is_numeric By: Thomas Mlynarczyk on Sun, 12 May 2013 17:05
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sun, 12 May 2013 17:38
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sun, 12 May 2013 17:46
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 12 May 2013 18:11
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sun, 12 May 2013 18:39
		Re: bug in is_numeric By: Jerry Stuckle on Sun, 12 May 2013 20:51
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sun, 12 May 2013 23:27
		Re: bug in is_numeric By: Jerry Stuckle on Mon, 13 May 2013 00:35
		Re: bug in is_numeric By: Thomas 'PointedEars' on Mon, 13 May 2013 09:07
		Re: bug in is_numeric By: Jerry Stuckle on Mon, 13 May 2013 13:02
		Re: bug in is_numeric By: Thomas 'PointedEars' on Mon, 13 May 2013 14:57
		Re: bug in is_numeric By: Thomas 'PointedEars' on Mon, 13 May 2013 15:10
		Re: bug in is_numeric By: Jerry Stuckle on Mon, 13 May 2013 17:52
		Re: bug in is_numeric By: Thomas 'PointedEars' on Mon, 13 May 2013 18:28
		Re: bug in is_numeric By: SwissCheese on Thu, 16 May 2013 22:28
		Re: bug in is_numeric By: Thomas 'PointedEars' on Thu, 16 May 2013 22:33
		Re: bug in is_numeric By: SwissCheese on Fri, 17 May 2013 02:34
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sat, 18 May 2013 08:28
		Re: bug in is_numeric By: Norman Peelman on Sat, 18 May 2013 12:00
		Re: bug in is_numeric By: Luuk on Sat, 18 May 2013 12:18
		Re: bug in is_numeric By: Tim Streater on Sat, 18 May 2013 12:20
		Re: bug in is_numeric By: Jerry Stuckle on Sat, 18 May 2013 12:47
		Re: bug in is_numeric By: The Natural Philosoph on Sat, 18 May 2013 13:05
		Re: bug in is_numeric By: Jerry Stuckle on Sat, 18 May 2013 14:16
		Re: bug in is_numeric By: Thomas 'PointedEars' on Sat, 18 May 2013 14:14
		Re: bug in is_numeric By: Sandman on Tue, 14 May 2013 08:34
		Re: bug in is_numeric By: fred on Tue, 14 May 2013 13:47
		Re: bug in is_numeric By: Denis McMahon on Tue, 14 May 2013 14:54
		Re: bug in is_numeric By: Sandman on Wed, 15 May 2013 06:05
		Re: bug in is_numeric By: Jerry Stuckle on Wed, 15 May 2013 10:27
		Re: bug in is_numeric By: Erwin Moller on Wed, 15 May 2013 11:11

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