On Mon, 14 Feb 2011 22:59:52 -0500, Jonathan M Davis <[email protected]>
wrote:
It's because an Array is not a range. Dynamic arrays are a bit special
in that
they're both a container and a range. An Array is just a container. But
honestly, you wouldn't really want it to work.
Dynamic arrays are not containers. They do not own the data they
reference, they just reference that data. In fact, the owner of the data
is really the runtime.
The naming of Array makes this a difficult thing to understand. An Array
owns its data, it manages the data, creates it, destroys it, and there is
no way to "slice" the Array into a smaller Array. It's a true reference
type. A builtin array is not really a container, so it really should be
named differently. But there's no way to change that.
However, this won't work for containers in general. If you pass an
Array, you're
passing the container. The passed in Array is identical to the original
(currently, Array is a struct with reference semantics thanks to internal
reference counting, but soon it will become a class and more obviously
have
reference semantics). As such, if you alter the passed in Array, you
alter the
original. So, if you were to continuously pop the front off of the
passed in
Array, you would be continually popping the front off of the original
Array. So,
a function like find would actually remove the front part of your Array
as it
processed it, and if what you were trying to find wasn't there, you'd
have an
empty Array. The way to fix this is to not have Array be a range.
Instead, you
have a helper type which is a range over it. You get that with the slice
operator.
This is a good way to explain it.
You don't have the problem with arrays that you'd have with user-defined
container types, because the semantics of arrays are a bit odd when you
copy
them. So, if anything were faulty, it would be the built in arrays, not
user-
defined container types like Array. It is quite handy to have arrays
work how
they work, however, so that's not likely to change.
What is faulty is that they are called arrays. They are slices.
-Steve
