Terminology: "reference" versus "pointer"

Emile van Sebille emile at fenx.com
Sat Sep 12 19:14:05 CEST 2015


On 9/12/2015 9:54 AM, Rustom Mody wrote:
> On Saturday, September 12, 2015 at 10:02:40 PM UTC+5:30, Steven D'Aprano wrote:
>> On Sat, 12 Sep 2015 02:42 pm, Random832 wrote:
>>
>>> Anyway, maybe we do need a term to distinguish Python/C#/Java pointers
>>> from C/C++ pointers - maybe call it a "non-arithmetic" pointer, since
>>> the key thing about it is you can't do pointer arithmetic on them to get
>>> the object "next to" the one it points at.
>>
>> How about *just don't call them pointers*? You know, since they aren't
>> pointers in the computer science sense.
>>
>> The Free On-line Dictionary of Computing defines "pointer":
>>
>>     1. <programming> An address, from the point of view of a
>>     programming language.  A pointer may be typed, with its type
>>     indicating the type of data to which it points.
>
> <snip>
>
>> Insisting that Python has pointers is like insisting that you use a text
>> editor by flipping bits. "What happens if I press Ctrl-X?" "Well, these
>> bits on the screen flip from black to white, these bits flip from white to
>> black, and these stay the same."
>>
>
> This is from the docs
> https://docs.python.org/3/library/functions.html#id
>
> id(object)
>
>      Return the "identity" of an object. This is an integer which is guaranteed to be unique and constant for this object during its lifetime. Two objects with non-overlapping lifetimes may have the same id() value.
>
>      CPython implementation detail: This is the address of the object in memory.

Quoting from above:

 >> The Free On-line Dictionary of Computing defines "pointer":
 >>
 >>     1. <programming> An address, from the point of view of a
 >>     programming language.

So, how does the CPython program access the contents given its 'address 
in memory'?  From the definition it would seem it's not a pointer, as 
from the perspective of the programming language, you can't get there 
from the id.

Look-ma,-no-pointers-ly y'rs,

Emile





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