diff options
Diffstat (limited to 'absl/container/node_hash_set.h')
| -rw-r--r-- | absl/container/node_hash_set.h | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/absl/container/node_hash_set.h b/absl/container/node_hash_set.h index ec9ab519..8cc4b624 100644 --- a/absl/container/node_hash_set.h +++ b/absl/container/node_hash_set.h @@ -64,7 +64,7 @@ struct NodeHashSetPolicy; // // * Supports heterogeneous lookup, through `find()`, `operator[]()` and // `insert()`, provided that the set is provided a compatible heterogeneous -// hashing function and equality operator. +// hashing function and equality operator. See below for details. // * Contains a `capacity()` member function indicating the number of element // slots (open, deleted, and empty) within the hash set. // * Returns `void` from the `erase(iterator)` overload. @@ -80,6 +80,19 @@ struct NodeHashSetPolicy; // libraries (e.g. .dll, .so) is unsupported due to way `absl::Hash` values may // be randomized across dynamically loaded libraries. // +// To achieve heterogeneous lookup for custom types either `Hash` and `Eq` type +// parameters can be used or `T` should have public inner types +// `absl_container_hash` and (optionally) `absl_container_eq`. In either case, +// `typename Hash::is_transparent` and `typename Eq::is_transparent` should be +// well-formed. Both types are basically functors: +// * `Hash` should support `size_t operator()(U val) const` that returns a hash +// for the given `val`. +// * `Eq` should support `bool operator()(U lhs, V rhs) const` that returns true +// if `lhs` is equal to `rhs`. +// +// In most cases `T` needs only to provide the `absl_container_hash`. In this +// case `std::equal_to<void>` will be used instead of `eq` part. +// // Example: // // // Create a node hash set of three strings |