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Re: bug in is_numeric [message #181340 is a reply to message #181339] Mon, 13 May 2013 00:35 Go to previous messageGo to previous message
Jerry Stuckle is currently offline  Jerry Stuckle
Messages: 2598
Registered: September 2010
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On 5/12/2013 7:27 PM, Thomas 'PointedEars' Lahn wrote:
> Jerry Stuckle wrote:
>
>> On 5/12/2013 2:39 PM, Thomas 'PointedEars' Lahn wrote:
>>> Jerry Stuckle wrote:
>>>> On 5/12/2013 1:38 PM, Thomas 'PointedEars' Lahn wrote:
>>>> > 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)
>>>> >
>>>>
>>>> Wrong, as usual.
>>>>
>>>> <snip>
>>>
>>> Intentionally misquoted, as usual.
>>
>> And exactly what is wrong with what I quoted?
>
> In contrast to what you stated, exactly *nothing* is wrong with it when
> properly quoted; that is, *in context*, which is the point. Giving you the
> benefit of a doubt, you appear to have severe difficulty understanding the
> concept of context as such and the importance of context in quotations
> specifically; it would be good if you could work on that.
>

That was the beginning of your reply. There was no previous context to
quote.

>> The rest of your trash
>
> Not everything that you choose to ignore or fail to understand is “trash”
> because of that.
>

No, but almost *everything* you say is pure tripe. You can't blame this
on the "context".

>> was based on this incorrect premise; it would be a waste of bandwidth to
>> repost your entire tripe.
>
> As showed by the PHP output that I posted further below, and that you
> snipped, the premise is _not_ incorrect. To elaborate:
>

The premise is completely incorrect. 'x11.11c' is NEVER considered a
numeric value, as several other people (including me) have shown. And
the '.' is NEVER an operator when within a quoted string.

> “.” would be considered a concatenation operator here; there is no other
> production of the PHP grammar that fits the source code better. Numeric
> literals must not start with “x” in PHP, which precludes the possibility
> that “.” would be parsed as a decimal point of the literal “x11.11” (which,
> giving you the benefit of a doubt, might have been your assumption drawing
> from other programming languages that you might know).
>

Nope. Not when it is within a quoted string.

> As a result, “x11“ would be considered a constant's identifier; because such
> a constant would likele be undeclared, it would be parsed as if it was a
> string value containing the characters of the would-be identifier as
> characters (see the PHP Notices in the test, and the generated output for
> proof of that).
>

Nope, not unless there was a define ('x11',...) statement previous to
this. It is a string - plain and simple. But you don't understand such
a simple concept.

> “11c” would be considered a constant identifier as well (and treated the
> same way) if it did not start with a decimal digit. Or it would be
> considered a decimal literal if it did not contain/end with “c” (allowed
> would only be “e” followed by a decimal literal, for the
> exponential/scientific decimal format). But as it does contain/end with “c”
> that is not in a hexadecimal literal, it is a *syntax error*. Therefore,
> the entire expression would not compile and the entire PHP program would not
> compile, being syntactically in error.
>

Wrong again. In PHP you have to have a define() statement to create a
constant. It is part of string. However, that's way beyond your
comprehension.

> We have now ascertained that, as Thomas Mlynarczyk stated, “x11.11c” cannot
> be a proper numeric literal in PHP (it would be an operation expression
> [that would not compile, but that is unimportant from here]). As that is
> the case, “'x11.11c'” also is not considered numeric in PHP, which is why
>

No, it is a string value, nothing more, nothing less.

> is_numeric('x11.11c')
>
> must return FALSE. By contrast, is_numeric('0x11') returns TRUE.
>

is_numeric('0x11') has nothing to do with the problem at hand.

> However, there appears to be an *actual* mismatch between PHP manual and
> implementation in said PHP version as
>
> is_numeric('0b11001001')
>
> returns FALSE when according to the manual it should return TRUE (binary
> integer literals are available since PHP 5.4.0 per the manual, and they do
> compile and properly evaluate in tests there.
>

Again, absolutely nothing to do with this problem.

>> [more flames]
>
> It is a pity that too often you are not able to master your emotions in
> order to participate in a factual discussion in a constructive way.
>
>
> PointedEars
>

It's a pity you are so stoopid that you can't understand even simple
concepts so as to be able to participate in an intelligent discussion.
I suggest you try washing dishes. It's more your speed.

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================

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