Yigal Chripun wrote:
On 19/10/2009 23:42, Andrei Alexandrescu wrote:
Yigal Chripun wrote:
here's an example of a well designed, consistent API:
http://www.gobosoft.com/eiffel/gobo/structure/index.html
This is a solid framework, unlike Java's containers which are a joke. I
disagree with some of Gobo's abstractions (e.g. I believe all containers
must be traversable and that primitives such as count() have no place in
a general container) but generally the framework seems to be very well
put together. It's a great source of inspiration for Phobos. Thanks very
much for the link.
Andrei
My understanding of this design is that they identified all the
orthogonal properties relevant to containers and that specific
containers are a composition of a specific set of such properties.
Eiffel has MI (different from the c++ implementation) which is helpful
if you already have suitable default implementations for these properties.
regarding "traversable" property:
what if I want a container for a non-ordered type? an example would be a
container of complex numbers, how would you traverse it?
what about hash tables?
Well as others mentioned, a hash table is traversable, just not in a
particularly ordered manner.
IMHO any container must offer at the very least (I'll use stylized
signatures):
1. Got any?
bool empty();
2. Iterate using at least a one-pass range
OnePassRange!E opSlice();
3. Remove some element from the container and give it to me
E removeAny();
4. Add an element to the container is possible
bool add(E);
5. Nuke
void clear();
I think any container must support these primitives in O(1), and I find
it difficult to think of a significant category of containers that can't
support them (but then there may as well be, so please join me in
thinking of that). A lot of stuff can be done with only these few methods.
Note that even though length() is not part of the interface (as is in
Gobo's library), it can be computed through iteration with a generic
algorithm. The idea is to not force containers to write that themselves
or ungainly cache the length.
Please let me know of any thoughts.
Andrei
