result1 ==On 11/02/2011 22:51, Simen kjaeraas wrote:
Bruno Medeiros <[email protected]> wrote:
In this code sample if the optimization is applied on the second call
to func, it would cause different code with be executed: the else
clause instead of the then clause. Obviously this is not acceptable
for an optimization, even if such code would be rare in practice.
Ah yes, I see now. I could argue that 'is' is cheating. :p
I believe actually, that pure is only said to promise that the returned
values should be such that func(args) == func(args), not accounting for
overloaded operators.
That still would not be guaranteed. In the example I mentioned before,
it already happens that
(result1 == result2) == false
I think that the concession that pure will be allowed to allocate memory
does inescapably remove some of the guarantees that pure functions offer
(like that one that the return value depends only on the arguments).
One possible fix to this would be to say that the allocated memory must
be temporary (used only during the execution of the pure function). Thus
you would not be able to return any newly-allocated value. But I don't
know if this further restriction is desirable or not. I don't remember
if this aspect of memory allocation in pure functions was
discussed/thought-out extensively or not. (it probably needs to)
--
Bruno Medeiros - Software Engineer
