cpp: make isl objects compatible with standard containers. about isl HOT 5 OPEN

The bindings are already C++11 of larger. Not sure if this would change anything regarding the separate file.

And yes, I think it would be great to systematically think about less-than and hashability. Your point of needing a std::hash for id was a certainly a good one.

from isl.

Sorry, I've mistaken that for the generator file, which is not C++11. Nevermind.

For hashes there are two options: either we can wrap around isl_*_get_hash() or just compute a hash of the pointer with the standard hashing function.

from isl.

This likely depends what you want. isl_*_get_hash gives identical hashes for different objects that model the same set. The pointer does not carry this information.

from isl.

Well, I think it is reasonable to expect hashes of logically equal (i.e. represent the same set) values to be equal.

from isl.

There are good reasons for expecting logical equality. On the other side, hashing can be expensive this way. Assume you insert a large isl::set into a hashtable and you first need to scan the full isl::set. I feel there is a tradeoff.

from isl.