Pure functions in D

[Christopher Wright]

Bruno Medeiros wrote:
> Walter Bright wrote:
>> http://www.reddit.com/r/programming/comments/72r6q/walter_bright_pure_functions_in_d/ 
>>
> 
> Interesting.
> 
>  >Parameters to a pure function can be mutable, but calls cannot be 
> cached or executed asynchronously if the arguments contain any 
> references to mutable data.
> 
> Cool, this amounts the same to the "partial pure"/"contextually pure" 
> idea Don and I discussed some time ago. Good to see you thought of the 
> same.
> 
> A few questions:
> 
> If a pure function can throw, is it required that it always throws given 
> the same inputs (and throwing the same Exception?).
> 
> Will memory allocation be considered pure?

Allocating heap memory affects global state, to whit, the garbage 
collector's state. I can't see how you can allow memory allocation.

You can call new, though, in a pure function, provided it's placement 
new or scope.