On Saturday, 30 March 2013 at 00:23:17 UTC, Jonathan M Davis
wrote:
On Friday, March 29, 2013 23:22:36 Tobias Pankrath wrote:
On Friday, 29 March 2013 at 22:13:31 UTC, Tobias Pankrath
wrote:
> Hello,
>
> the following struct is not an input range because you can't
> call popFront on it, however I'd say you should be able to.
>
> struct Wrapper {
>
> int[] _data;
> alias _data this;
>
> }
>
> Bug or intended behaviour?
>
> Thank you!
The reason seems to be that, while
is(DynamicArrayTypeOf!Wrapper
== int[]) holds, isDynamicArray!Wrapper equals false, because
isDynamicArray checks for !isAggregateType!Wrapper. Looks like
a
bug isDynamicArray to me.
No, it is most definitely _not_ a bug in isDynamicArray. The
isX traits in
std.traits specifically check for exact tyes and _not_ implicit
conversions. If
it's a bug, it's in the fact that isDynamicArray is used in
popFront's
template constraint. Whether or not Wrapper should be treated
as a range is up
for some debate (implicit conversion tends to cause big
problems with template
constraints, as it becomes far too easy to have constraints
which pass and yet
the function doesn't actually work with the type), but the main
problem is
that front and popFront for arrays don't agree on what they
should work with -
front takes T[] and popFront checks isDynamicArray. So, front
works with
implicit conversion, and popFront doesn't, and that needs to be
fixed. But the
bug is in front/popFront, not isDynamicArray.
I believe that there was a thread on this recently (started by
monarch_dodra
IIRC), so you can look for that discussion for more information
if you'd like.
- Jonathan M Davis
Yes, you are most probably right that the bug is not in
isDynamicArray. However DynamicArrayTypeOf and isDynamicArray are
rather inconsistent since DynamicArrayTypeOf does not check exact
types.
