On Wednesday, 9 March 2016 at 16:53:08 UTC, Xinok wrote:
On Wednesday, 9 March 2016 at 15:39:55 UTC, rcorre wrote:
Still curious as to why it fails; maybe the range is getting
copied at some point? I guess I need to step through it.
That's my suspicion as well. It seems that OnlyResult is
pass-by-value so every time it gets passed to another function,
it creates a copy of all the elements. A simple solution is to
provide a wrapper type which refers to the elements in the
original container.
However, I'm going to argue that the sort function is fine but
the modifications you made to OnlyResult are incorrect. I tried
running your example of only(...).sort but got a compilation
error. Similarly, trying to sort a static array also gives a
compilation error. However, if I slice the static array before
passing it to sort (thus passing by reference), then it works
just fine.
Got it. sort calls to quicksort (for unstable, at least) which
uses swapAt. swapAt takes the range by value, so it just swaps
the values in its local copy. The original OnlyResult is
untouched. I guess a static array slice maintains a pointer to
the underlying array (which is why returning one from a function
errors with 'escaping reference to local variable').
Meanwhile, I've realized my code probably doensn't need to remove
duplicates anyways, so its a moot point, but still an interesting
discovery :)
