How to fake pure

[Timon Gehr]

On 4/8/25 17:07, Guillaume Piolat wrote:
> On Tuesday, 8 April 2025 at 14:00:56 UTC, Jonathan M Davis wrote:
>> Of course, I'm also increasingly of the opinion that pure was a 
>> mistake in general, because it does almost nothing in practice but 
>> routinely doesn't work with straightforward code - and it's definitely 
>> one of those attributes which gets in way when code needs to be 
>> refactored
> 
> 
> And you really need pureMalloc to be applicable, hovewer it's a lie 
> since the GC and malloc obviously have global state.

It's not really a lie. This is just a confusion of levels of 
abstraction. Purely functional languages use memory allocators too, and 
they can also run out of memory.

The underlying problem here is that `pure` in D does not have a formal 
semantic meaning and there are some highly questionable choices such as 
dependencies on memory addresses and FPU state being considered `pure`.

In any case, casting a memory allocator to `pure` should be fine. Any 
reasonable definition of `pure` we can come up with in the future would 
be compatible with that.