How to append or prepend on a Scala mutable.Seq
There's something I don't understand about Scala's collection.mutable.Seq
. It describes the 开发者_JAVA百科interface for all mutable sequences, yet I don't see methods to append or prepend elements without creating a new sequence. Am I missing something obvious here?
There are :+
and +:
for append and prepend, respectively, but they create new collections — in order to be consistent with the behavior of immutable sequences, I assume. This is fine, but why is there no method like +=
and +=:
, like ArrayBuffer
and ListBuffer
define, for in-place append and prepend? Does it mean that I cannot refer to a mutable seq that's typed as collection.mutable.Seq
if I want to do in-place append?
Again, I must have missed something obvious, but cannot find what…
Mutability for sequences only guarantees that you'll be able to swap out the items for different ones (via the update
method), as you can with e.g. primitive arrays. It does not guarantee that you'll be able to make the sequence larger (that's what the Growable
trait is for) or smaller (Shrinkable
).
Buffer
is the abstract trait that contains Growable
and Shrinkable
, not Seq
.
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