On Friday, 16 January 2015 at 17:13:33 UTC, Joseph Rushton
Wakeling wrote:
On Friday, 16 January 2015 at 17:09:47 UTC, Tobias Pankrath
wrote:
While the first example is indeed problematic, this one
actually is not. If this does not print the same 10 numbers
every time, your save method is wrong.
Regardless of being a reference type or not it has to clone
the RNG state or it doesn't do its job.
I think you've misunderstood what I was getting at, probably
because I didn't explain myself well.
Obviously it's correct that the second function example should
print out the same thing 10 times. However, what is wrong is
that at the end of that function, the source range -- if a
reference type -- should itself have been popFront'ed a
sufficient number of times, but it hasn't been.
That's a design fault in the function implementation, which
doesn't take into account the desirable behaviour (for the
caller) if the range given to the function is a reference type.
Ah, now I understand you. Since copy-construction is undefined
for ForwardRanges, you cannot guarantee this. Things would be
better, if we had required that this(this) does the same as .save
or must be @disabled.
Than it would be clear that you either had to use a reference or
a pointer as argument to the function.
