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Posted by David Haynes on 06/25/06 09:39
Tony Marston wrote:
> "David Haynes" <david.haynes2@sympatico.ca> wrote in message
> news:Tvkng.22537$oG2.21662@fe26.usenetserver.com...
>> Tony Marston wrote:
>>> "Jerry Stuckle" <jstucklex@attglobal.net> wrote in message
>>>> Actually, things like private declarations are very important. They are
>>>> unimportant only to those who don't understand OO programming - or those
>>>> who are sloppy in their implementations.
>>> You don't *need* private declarations. Code will work just as well
>>> without them.
>>>
>> What the heck! Let's just throw away multiply and divide. We don't *need*
>> them. We can just use add and subtract.
>>
>> Heck! Why do we need subtract? We can just add negative values.
>>
>> Hey! Assembler works well without private declarations. Let's just pitch
>> PHP all together.
>>
>> The point is that constructs are added to language to assist in the
>> functionality and maintainability of programs written in that language.
>> The introduction of private and protected adds to the maintainability both
>> through its inherent protection capabilities and its clarity of intent for
>> the maintainer.
>>
>> Now if PHP could just get polymorphism...
>
> OOP with PHP already has polymorphism. You obviously don't know what
> polymorphism means.
>
Tony:
PHP5 has weak polymorphism but not true polymorphism in the sense that
it is used in OOP.
You cannot, for instance, have multiple constructors for an object where
the number of the arguments to the constructor are variable. Yes, you
may supply default values to 'optional' arguments but consider this example:
class Foo {
function __construct($one, $two="two", $three="three") {
I cannot instantiate this object as new Foo($one, $three) since there is
no typing on the arguments and, therefore, no signature for a 'one,
three' contructor. Nor could I define multiple __constructor() methods
to allow for the new Foo($one, $three) case.
This type of action is common in other OOP languages such as Java and C++.
To add to the confusion from an OOP programmer's viewpoint, in order to
invoke the 'default' value for $three, I *must* supply a value for $two.
That is, new Foo($one, , $three) is syntactically illegal and there is
AFAIK no way to specify that we want $two to take its default value
while supplying a value for $three.
So, maybe its not me who is unclear on the concept of polymorphism...
-david-
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