purity and memory allocations/pointers

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On Saturday, 3 August 2013 at 16:47:52 UTC, Timon Gehr wrote:
> On 08/03/2013 05:59 PM, monarch_dodra wrote:
>> One last question: Pointers.
>>
>> int get(int* p) pure
>> {
>>     return *p;
>> }
>>
>> void main()
>> {
>>     int i = 0;
>>     auto p = &i;
>>     get(p);
>> }
>>
>> Here, get, to me, is obviously not pure, since it depends on 
>> the state
>> of the global "i". *Where* did "get" go wrong? Did I simply 
>> "abusively"
>> mark get as pure? Is the "pure" keyword's guarantee simply 
>> "weak"?
>> ...
>
> Yes, it's weak.

It depends on whether you think a pointer dereference is pure or 
not (I don't know the answer). That aside, as long as get doesn't 
modify the value at *p or change what p points to, this is 
strongly pure (i.e., the academic definition of purity).