Memory allocation purity

[Steven Schveighoffer via Digitalmars-d]

On Mon, 19 May 2014 13:31:08 -0400, Ola Fosheim Grøstad  
<ola.fosheim.grostad+dlang at gmail.com> wrote:

> On Monday, 19 May 2014 at 17:11:43 UTC, Steven Schveighoffer wrote:
>> It shouldn't matter. Something that returns immutable references, can  
>> return that same thing again if asked the same way. Nobody should be  
>> looking at the address in any meaningful way.
>
> I think this is at odds with generic programming. What you are saying is  
> that if you plug a pure function into an algorithm then you have to test  
> for "pure" in the algorithm if it is affected by object identity.  
> Otherwise, goodbye plug-n-play.

I think I misstated this, of course, looking at the address for certain  
reasons is OK, Object identity being one of them.

But some of the tricks being detailed here as "proof" that we cannot  
memoize are not really valid code.

Returning the same immutable object, when called with the same immutable  
parameters, should never cause a break in code, pure or not.

-Steve