Ranges and random numbers -- again

[Jonathan M Davis]

On Tuesday, June 18, 2013 10:39:38 Andrei Alexandrescu wrote:
> On 6/18/13 10:16 AM, H. S. Teoh wrote:
> > I say again that RNGs being passed by value is a major BUG. The above
> > situation is a prime example of this problem. We *need* to make RNGs
> > passed by reference. For situations where you *want* to duplicate a
> > pseudo random sequence, an explicit method should be provided to clone
> > the RNG. Duplication of RNGs should never be implicit.
> 
> Occasionally copying a RNG's state is useful, but I agree most of the
> time you want to just take a reference to it.
> 
> I think a good way toward a solution is
> http://d.puremagic.com/issues/show_bug.cgi?id=10404.

That may be a good way to go about it, but the default such as what rndGen 
returns really should be a reference type, and only ranges whose state can 
actually be copied such that continuing to iterate over them gives the same 
values should be forward ranges IMHO. Using Class!T might be able to make it 
so that we can avoid needing a std.random2, but we'll probably still need some 
minor code breakage in there somewhere.

- Jonathan M Davis