Purity (D2 standard libraries / object.d)

[Christopher Wright]

Bill Baxter wrote:
> But the call for a memoization thingy I just don't get.  No way that
> should be a compiler feature, just far too many ways to memoize with
> too many different tradeoffs.  And a memoizing wrapper function
> basically loses nothing in terms of expressiveness.
> 
> --bb

The ability for you to memoize a pure function and get a pure function 
as a result. Your pure functions can't use the memoized version of the 
pure function.

This means you might have to use a lot more memoization wrappers.