Proposal: Relax rules for 'pure'

[Steven Schveighoffer]

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.

-Steve