On Friday, 4 December 2015 at 06:05:55 UTC, Tofu Ninja wrote:
On Friday, 4 December 2015 at 03:37:10 UTC, Andrei Alexandrescu
wrote:
On 12/3/15 10:29 PM, Jack Stouffer wrote:
On Friday, 4 December 2015 at 02:21:12 UTC, Andrei
Alexandrescu wrote:
On 12/03/2015 09:10 PM, Idan Arye wrote:
The complexities of the operations is a property of the
data structure
being used. If each collection type will have it's own set
of method
names based on the complexity of operations on it, we won't
be able to
have templated functions that operate on any kind of
collection(or at
the very least, these functions will be really tedious to
code).
Your premise is right but you reach the negation of the
correct
conclusion. -- Andrei
How so? If a singly linked list and a doubly linked list have
two
different method names for the same operation, then they
cannot be
easily templated.
Took me a while to figure. There's a hierarchy of operations,
e.g. if a collection implements insert, it automatically
implements linearInsert. And so on. The collections framework
provides these defaults, so client code that needs quick
insert uses insert, whereas code that's fine with a linear
upper bound uses linearInsert and captures both.
Another way to look at it: in STL container-independent code
is near impossible because different containers use the same
signature for operations that are different (either wrt
iterator invalidation or complexity). My design avoids that by
giving distinct operations distinct names.
Andrei
This sounds really complicated to use? What are the benefits?
When would a generic algorithm even need to know the complexity
of the container?
Also maybe a simpler idea would just be to annotate the the
operations with there complexity with UDAs. That way things
that really care about the complexity can get it, and those who
don't can ignore it. It has the benefit of being self
documenting as well.
Ranges are a good example - they provide only the operations thay
can efficiently implement. For example forward ranges could
provide random access but at the cost of linear running time.
std.containers provides the `elem in container` operation only if
they can implement it in logarithmic time or faster.
The fact that you can't use opIn for DList or Array is very good,
because it prevents you from writing inefficient genric code.
You're algorithm will manifest that it can only work with
containers provide efficient operations and because of that you
can be sure what its time complexity would be.
You should choose a specific data structure only because you can
efficiently implement the algorithm you have in mind with it.
One of worst examples of the opposite is .Count extention method
in .NET (which happens to have the same name as .Count member
function of ICollection - one of the most used (often implicitly)
interfaces), which has linear running time. The most horrible
thing I have seen!
