Posted by Steve on 09/25/07 13:35

"Jerry Stuckle" <jstucklex@attglobal.net> wrote in message
news:i6WdnSgveO9ee2XbnZ2dnUVZ_gadnZ2d@comcast.com...
> Steve wrote:
>> "Jerry Stuckle" <jstucklex@attglobal.net> wrote in message
>> news:VLWdnbBpwNDwzmXbnZ2dnUVZ_gmdnZ2d@comcast.com...
>>> Shelly wrote:
>>>> "Jerry Stuckle" <jstucklex@attglobal.net> wrote in message
>>>> news:J_ednRJzLNIw3GXbnZ2dnUVZ_hGdnZ2d@comcast.com...
>>>>> Shelly wrote:
>>>>>> "gosha bine" <stereofrog@gmail.com> wrote in message
>>>>>> news:46f823bf$0$31121$6e1ede2f@read.cnntp.org...
>>>>>>> Shelly wrote:
>>>>>>>> "Steve" <no.one@example.com> wrote in message
>>>>>>>> news:r6VJi.36$Nr6.32@newsfe05.lga...
>>>>>>>>> "Joe" <joe@faceh.com> wrote in message
>>>>>>>>> news:1190663828.772978.15800@22g2000hsm.googlegroups.com...
>>>>>>>>>> I am just starting to use Object Oriented PHP coding, and I am
>>>>>>>>>> seeing
>>>>>>>>>> quite often the following (this example taken from a wiki):
>>>>>>>>>>
>>>>>>>>>> $wakka =& new Wakka($wakkaConfig);
>>>>>>>>>>
>>>>>>>>>> What exactly is the =&, and why is it different from = ?
>>>>>>>>> well, better syntax would have helped. it should read ' $something
>>>>>>>>> = &$variable'. in this context, & means 'a reference to the memory
>>>>>>>>> location where the value is stored'. without the &, it means 'a
>>>>>>>>> copy of the value of the variable'.
>>>>>>>>>
>>>>>>>>> clear as mud? rather than explain memory, let me have you do this:
>>>>>>>>>
>>>>>>>>> $variable = 'hello';
>>>>>>>>> $reference = &$variable;
>>>>>>>>> $variable = 'world';
>>>>>>>>> echo '<pre>' . print_r($reference, true) . '</pre>';
>>>>>>>>> $reference = 'good-bye';
>>>>>>>>> echo '<pre>' . print_r($variable, true) . '</pre>';
>>>>>>>>>
>>>>>>>>> unset($variable);
>>>>>>>>> unset($reference);
>>>>>>>>>
>>>>>>>>> $variable = 'hello';
>>>>>>>>> $reference = $variable;
>>>>>>>>> $variable = 'world';
>>>>>>>>> echo '<pre>' . print_r($reference, true) . '</pre>';
>>>>>>>>> $reference = 'good-bye';
>>>>>>>>> echo '<pre>' . print_r($variable, true) . '</pre>';
>>>>>>>>>
>>>>>>>>> the first example, BY REFERENCE, means that both $variable and
>>>>>>>>> $reference point to the same memory location. changing one but
>>>>>>>>> using the other makes no difference - using either will have the
>>>>>>>>> same effect.
>>>>>>>>>
>>>>>>>>> the second, BY VALUE, means that each variable points to two
>>>>>>>>> different locations in memory. the only time they will be equal is
>>>>>>>>> when setting them so. once you modify one of them, you have done
>>>>>>>>> so idependently of the other - changing one has no effect on the
>>>>>>>>> other.
>>>>>>>>>
>>>>>>>>> hope that makes more sense.
>>>>>>>> That was probably the single most unique new concept (pointers and
>>>>>>>> address-of) I had conquer when (os so many years ago) I learned C,
>>>>>>>> coming from a Fortran background as I did.
>>>>>>>>
>>>>>>>> Shelly
>>>>>>> php references have nothing to do with C-alike pointers.
>>>>>>>
>>>>>>> Please read the chapter called "references are not pointers" in the
>>>>>>> manual.
>>>>>>>
>>>>>> Yeah, yeah. We still are talking about address-of and not value-of.
>>>>>> So there is no explicit pointer variable as there is in C. So what?
>>>>>>
>>>>>> Shelly
>>>>> No, it's not address-of, either in PHP or C++. It's more "alias-of".
>>>> ...and by alias of you mean another way of referencing the same place
>>>> in memory that contains the value as the thing it is aliasing. --- aka
>>>> address-of. Change the value contained in the "reference" and the
>>>> value of the "referenced" changes. Change the value located at the
>>>> "address of" and the value of the other variable changes. Six of one,
>>>> a half dozen of the other. *ptr->foo=junk does the same thing as
>>>> saying foo=junk. Also fee=&foo and *fee=junk does the same thing.
>>>> (It has been about seven years six I did any C coding (so my memory of
>>>> exact syntax may be a little off), but it all comes down to the Bard --
>>>> "a rose by any other name....".
>>>>
>>> Well, of course everything in the computer has an address. But you
>>> should not consider it an address in PHP (PHP doesn't HAVE addresses).
>>> It might be referencing a hash value in a table, for instance, and that
>>> table may have no fixed address.
>>
>> well, when dealing with a topic that is hard to explain as it is to a
>> newbie who could care less about what php does behind the scenes, a good
>> common ground language would be pointers since they are in most other
>> modern languages.
>>
>
> Well, a newbie has no idea what a "pointer" is. Or what it does behind
> the scenes. Many people have never programmed in C/C++, for instance -
> and the majority of other languages (Java, Fortran, COBOL, Perl, PASCAL,
> Basic... the list goes on) have no concept of pointers.
>
> Pointers are a VERY DIFFICULT subject for people who have never been
> exposed to them, no matter what their experience. In my C and C++
> classes, it is the most difficult concept for programmers experienced in
> non-pointer languages to grasp. In fact, most beginning programmers have
> an easier time than experienced ones.
>
> Much better to use non-technical terms, such as "alias".

very good point. however, i would hope that if a term (the only technical
one i gave) were unfamiliar to the op, he'd google it and find a full
definition with examples. that's just too much to cover in here. anyway, if
i use a non-technical term like 'alias', then i'm stuck explaining
everything to the op in here.

again, that's why i focused on the example rather than a full-blown
explanation.

>> i don't think the op is familiar with it anyway based on the way the
>> question was posed. that's why my first response demonstrated the
>> behavior rather than a technically correct response - one that would have
>> been lost any way, on the op.
>>
>
> And unnecessarily complicated the description.

actually, the first description was as reduced as possible while still not
becoming inaccurate. it really was a setup for the example. he has something
to look at to figure out the description based on what he observes. you do
have a good point though...i could have said 'pointer', 'reference', and
then described 'alias' instead. that way he could google that if need be.

>>> Additionally, in C++, it is NOT an address. You cannot change what item
>>> is being referenced in C++, for instance. It is truly an alias.
>>
>> actually, if you want to get technical, each variable points to an
>> address in memory that address may contain either data for the datatype
>> specified, or it may contain a pointer to another address...that may
>> contain either data for the datatype specified, or it may contain a
>> pointer to another...
>>
>
> Sure. But there is a distinct difference between a pointer and a
> reference. COBOL and FORTRAN both have variables. They both have
> something which acts like references. But they don't have pointers.
>
> PHP has references. It does not have pointers. What goes on under the
> covers is immaterial.

again, let me reiterate:

>> but, who gives a shit really. we're trying to get a point across that is
>> not simply made either way. is this helping the op, or edifying someone
>> else?


> The person who doesn't understand because you unnecessarily complicated
> the explanation with technical gobbly-gook?

i explained it the best i could...and i gave an example. i think that is
sufficient. what i don't get is the fact that you make that statement, all
the while doing a techie-deepthrought about stuff that is far above the op's
paygrade and doesn't even address HIS question. you are addressing what you
though was OUR lack of knowledge in C++ and php. i don't see how this
benefitted the op, nor do i see you quickly spit-shining your kettle...my
pot had just come out of the washer and was fairly clean on this topic.

>>> The difference being in C++ you do have addresses - they are used in
>>> pointer variables. And you can change the address (contents of the
>>> pointer) to point at another location in memory.
>>
>> and this is C++? btw, did you not see me change the variables in my
>> example from being references to independent 'memory locations'. don't
>> get technical here, we're talking about behavior. i did exactly what you
>> said php doesn't have the ability to do...if i understand you correctly
>> here.
>>
>
> I was discussing C++ implementation with Shelly, not your code.

i know, and i don't care about my code. what you said was:

"Well, of course everything in the computer has an address. But you
should not consider it an address in PHP (PHP doesn't HAVE addresses).
It might be referencing a hash value in a table, for instance, and that
table may have no fixed address.

Additionally, in C++, it is NOT an address."

i read that as a connected comparison. that was my attempt to show that the
behavior could be emulated.

>>> *ptr->foo = junk is NOT the same as foo=junk. *ptr->foo is pointing to
>>> a class or structure member (class/structure type unknown) named "foo".
>>> foo=junk is referencing a non-class/structure variable. You could say
>>> *ptr=junk, but only if ptr contains the address of foo.
>>
>> arguing his example gets you no where since his point is that you can get
>> the same *behavior* from php in most cases that you can in C++ regarding
>> references. if you want to go off on semantics, fine. however, remember
>> that php is a different animal than C++. that means, in most cases,
>> you're going to be comparing apples to oranges.
>>
>
> Yes, I know they are different. I am using C++ as an example because it
> has both pointers and references. It provides a valid comparison between
> the two. You can't make that comparison in PHP because it doesn't have
> pointers.

which is my whole point! C++ is being compared to PHP *because* php doesn't
have pointers...yet, the behavior is so similar that it becomes a matter of
semantics in most cases. still however, such a comparison is still apples
(c++) to oranges (php).

if you want me to use 'alias' instead of 'pointer', i'd consider it...same
with 'reference'. if i don't, then don't go all psycho...give me the exact
laymens terminology you think i should use. either way, for the question at
hand, there are only semantic differences and getting this technical with
people who already understand C++ is not helping anyone. the only thing that
would, is what definition of & would most make jerry comfortable.


>>> Additionally, in C++ you must have an exact match between types on each
>>> side - no conversions (i.e. int->double) allowed. References allow
>>> conversions (casting is not a conversion!).
>>
>> this would be an apple and an orange example, case in point! do you
>> expect *any scripting* language to *require* strong datatyping? that's
>> one of the strengths of scripting languages.
>>
>
> Not at all. It's a difference between pointers and references.
>
>> further, are you fully prepared to discuss in a meaningful way to the op,
>> how memory works, what conversions are and what casting is...not just how
>> php does any of them, but C++ also?
>>
>
> I sure can. Can you?

prepared, yes...willing to, no. i think i may just be more pragmatic about
the whole matter. a post the size of a small novel is not generally a
welcomed thing.

>>> I could continue - but there are significant differences between
>>> pointers in references in C++.
>>
>> that's great, however, we're talking about php. essentially, the behavior
>> is such, in this example, that making any distinction is just semantics
>> and very useless to the op.
>>
>
> We are talking about the differences between pointers and references,
> using a language which has both. PHP doesn't have pointers.

yet the *behavior* in this situation is identicle to pointers in C++. i'm
lost on any further argument you've got since the paygrade of the op
couldn't care less about the technicality of it all.

>>>> You say pot-tay-to and I say po-tah-to.
>>>>
>>>> Shelly
>>> Not at all. It is quite important to keep those straight, as I tell my
>>> C++ students.
>>
>> good for them that they have you, i suppose. i'm sure, being the seasoned
>> teacher that you are, you wouldn't dare cover such a topic on day one,
>> would you?
>>
>> ;^)
>
> No, we don't normally get into it until the afternoon of day 2.
>
> But then we do an entire C++ course in 5 days. It's what corporations
> want. And I've been doing it for almost 17 years now.

ROFLMFAO! and then they jump right into developing mission critical
applications, right?

i spent 3 semesters in the university learning C++. that was what the
UNIVERSITY wanted...they're more picky about their reputation, i suspect.

5 days. wow, i bow to your amazing talents jerry!

[Back to original message]