More tricky range semantics

[Dicebot via Digitalmars-d]

On Friday, 16 January 2015 at 00:58:34 UTC, Joseph Rushton 
Wakeling via Digitalmars-d wrote:
> On 16/01/15 00:24, Andrei Alexandrescu via Digitalmars-d wrote:
>> That's right. To simplify the problem space we might decree 
>> that forward (or
>> better) ranges with reference semantics are not allowed. -- 
>> Andrei
>
> That would seem to place significant restrictions on the 
> ability to define effective random number generators and 
> related functionality ... ?

Why RNG would be a forward range as opposed to just input range?