Memory allocation purity

[via Digitalmars-d]

On Monday, 19 May 2014 at 18:33:55 UTC, Steven Schveighoffer 
wrote:
> Anything that uses the order of unrelated addresses is 
> incorrect outside of the heap code itself.

Nah, not on modern archiectures without GC compaction.

> Then you should have no problem producing an example, right?

I did. Besides, I think language constructs should be proven 
sound a priori, not post mortem...

> The whole POINT of pure functions is that it will return the 
> same thing. The fact that it lives in a different piece of 
> memory or not is not important. We have to accept that. Any 
> code that DEPENDS on that being in a different address is 
> broken.

Which neans you cannot safely plug a pure function into a generic 
algorithm unless it testsfor purity.

> For instance, I would consider it fully possible and 
> reasonable, and to only break already-broken code (except for 
> testing implementation, which would have to change anyway), to 
> make idup just return the argument if the argument is immutable.

That could easily break sound code that need guards with 
different identities.