Add hashing support compatible with std::hash #11
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
brodeuralexis
commented
Aug 12, 2025
brodeuralexis
commented
Aug 12, 2025
brodeuralexis
force-pushed
the
feature/hash
branch
from
655d274 to
d01f3e4
Compare
brodeuralexis
commented
Aug 13, 2025
|
|
||
| template <> struct hash<::fine::Atom> { | ||
| size_t operator()(const ::fine::Atom &atom) noexcept { | ||
| return std::hash<std::string_view>{}(atom.to_string()); |
There was a problem hiding this comment.
To use *atom.term instead would require a rework of fine::Atom.
If receiving the atom from a NIF parameter, atom.term is std::nullopt. The only time when this is not the case is when atoms are globals and initialized during the load NIF callback.
There was a problem hiding this comment.
I think hashing the string is good!
jonatanklosko
approved these changes
Aug 14, 2025
There was a problem hiding this comment.
Looks great! There are a few conflicts after #10. Let's also remove the _test suffix here too :)
This is related to elixir-nx#10, and will allow `fine::Atom`s and `fine::Term`s to be used as `std::map`, and `std::unordered_map` keys.
PHASH2 is guaranteed to be stable across ERTS instance boundaries, hence making this hashing algorihtm more stable. This change is expected to reduce the friction for users, as terms will always hash equal, no matter the ERTS version and instance.
Now, only `std::hash` is supported to hash `fine::Term` and `fine::Atom` data structures. Due to the way `fine::Atom` is implemented, we cannot delegate to `enif_hash` to hash an atom, but must instead hash the atom's string representation.
brodeuralexis
force-pushed
the
feature/hash
branch
from
d01f3e4 to
0a799cf
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This will allow
fine::Atoms andfine::Terms to be used asstd::map, andstd::unordered_mapkeys if merged with #10.