Proposal: Relax rules for 'pure'

[Andrei Alexandrescu]

On 9/23/10 15:25 CDT, Don wrote:
> Steven Schveighoffer wrote:
>> On Thu, 23 Sep 2010 08:47:36 -0400, Robert Jacques <sandford at jhu.edu>
>> wrote:
>>
>>> On Thu, 23 Sep 2010 02:51:28 -0400, Don <nospam at nospam.com> wrote:
>>>
>>>> Jesse Phillips wrote:
>>>>> Steven Schveighoffer Wrote:
>>>>>> If we can define weakly pure functions this way, they most likely
>>>>>> will be way more common than unpure functions. I know I avoid
>>>>>> accessing global variables in most of my functions. Think about a
>>>>>> range, almost all the methods in a range can be weakly pure. So
>>>>>> that means you need to mark every function as pure.
>>>>
>>>> I think that's true. I/O is impure, but most other things are not.
>>>
>>> The GC also impure :)
>>
>> The GC must be assumed to be pure even though it's not. Otherwise,
>> pure functions can't do any heap allocation, and that makes them
>> pretty useless in a garbage collected languages.
>>
>> In functional languages, allocating memory is usually considered pure.
>
> In the D spec, it already says that 'new' is considered pure.

Which is wrong :o(. new invokes the constructor, which may do a variety 
of impure things.

Andrei