On 8/18/14, 1:44 AM, Peter Alexander wrote:
On Monday, 11 August 2014 at 03:29:56 UTC, Andrei Alexandrescu wrote:
[...] can be implemented generically for ranges that offer
front as a reference:
bool sameFront(R1, R2)(R1 r1, R2 r2) {
return &r1.front == &r2.front;
}
This doesn't work for ranges that visit the same element twice, e.g.
cycle(arr).take(arr.length + 1)
[0, 0].map!(i => arr[i])
Correct. Though maybe that's a good thing - rotating a cycle is unlikely
to produce something interesting.
I suspect most ranges will have to implement the sameFront primitive
manually, usually forwarding to the underlying range.
Only those that return rvalues from front.
Related: most mutating algorithms won't work for these kinds of ranges,
as we usually presume lvalue ranges never visit the same lvalue twice.
Perhaps this needs to be mentioned on affected algorithms?
Looks like a benign effect to me.
Andrei
