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Re: Different ways of representing "address" arguments

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"Thomas J. Gritzan" <phygon_antispam@gmx.de> wrote in message 
news:j46e3v$1r9$1@newsreader4.netcologne.de...
> Am 06.09.2011 18:04, schrieb Paul:
>> On Sep 6, 7:57 am, Goran<goran.pu...@gmail.com>  wrote:
>>> On Sep 5, 3:11 pm, "Jarrick Chagma"
>>>
>>> <Jarrick.Cha...@your.mind.gmail.com>  wrote:
>>>> I am new to C++ and have a basic question.  What is the semantic 
>>>> difference
>>>> between these two:
>>>
>>>> A) void foo(const int&i)
>>>> B) void foo(int *i)
>
> The const in A) applies to the referred to integer. In A) you cannot 
> change the value, while in B) you can change the pointed to value and the 
> pointer itself.
>
> (well, you can only change the local copy of the pointer, but not the 
> pointer in the calling function.)
>
>>>> AFAICT, both will result in the address of an integer argument being 
>>>> passed
>>>> to foo()
>>>> and in both cases the address cannot be modified.  Are there any
>>>> differences other than that i will need to be dereferenced in (B)? 
>>>> Which is
>>>> preferred?
>
> Prefer references unless you need pointer semantics. Prefer const unless 
> you need to modify.
>
>>> IMHO, if you see a pointer in a well-designed C++ code, it means
>>> there's a program state where said pointer can be null. That also
>>> means dealing with said null.
>>>
>> There is also the case where polymorphic behavour is expected.
>> The function may take a Shape pointer parameter type, where a Circle
>> or a Polygon is expected.
>
> Goran wanted to point out a difference between pointers and references.
>
> A reference cannot (legally) be null like a pointer, but polymorphic 
> behaviour works equally with references and pointers.
>
Yes I realise he was pointing out the difference between pointers and 
references. I was mainly responding to what he said about seeing a pointer 
in code means there will be a null state someplace, which is actually what I 
usually think myself. I was looking for a senario where this assumption is 
not always a prudent assumption. As you correctly pointed out my 
polymorphism example was not an ideal scenario as I was overlooking the fact 
that this can also be done using references.

Apart from the obvious scenario of re-allocating a different object to the 
pointer, and the benefits of having a possible null. There is another 
scenario where it may be beneficial to prefer a pointer over a reference 
thus it is not always prudent to assume the pointer may be null. That is 
when the argument is a pointer to an array. 


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[n00b] Different ways of representing "address" arguments "Jarrick Chagma" <Jarrick.Chagma@your.mind.gmail.com> - 2011-09-05 23:11 +1000
  Re: Different ways of representing "address" arguments Saeed Amrollahi <amrollahi.saeed@gmail.com> - 2011-09-05 06:47 -0700
  Re: Different ways of representing "address" arguments gwowen <gwowen@gmail.com> - 2011-09-05 06:59 -0700
  Re: Different ways of representing "address" arguments Goran <goran.pusic@gmail.com> - 2011-09-05 23:57 -0700
    Re: Different ways of representing "address" arguments Paul <pchristor@yahoo.co.uk> - 2011-09-06 09:04 -0700
      Re: Different ways of representing "address" arguments "Thomas J. Gritzan" <phygon_antispam@gmx.de> - 2011-09-07 02:32 +0200
        Re: Different ways of representing "address" arguments "Paul" <pchristor@yahoo.co.uk> - 2011-09-09 01:20 +0100
      Re: Different ways of representing "address" arguments Goran <goran.pusic@gmail.com> - 2011-09-07 00:01 -0700
        Re: Different ways of representing "address" arguments Paul <pchristor@yahoo.co.uk> - 2011-09-07 05:09 -0700
  Re: [n00b] Different ways of representing "address" arguments Bart van Ingen Schenau <bart@ingen.ddns.info> - 2011-09-06 13:19 +0200
    Re: Different ways of representing "address" arguments James Kanze <james.kanze@gmail.com> - 2011-09-06 15:29 -0700
  Re: Different ways of representing "address" arguments Joshua Maurice <joshuamaurice@gmail.com> - 2011-09-08 18:53 -0700

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