This module defines pure hash tables. All operations are non-destructive: Any "change" to a hash table (adding/deleting elements) produces a new hash table. Copying is avoided as much as possible, i.e., the old and new tables share values. This may lead to surprises if variables in the table are bound later on (or if they are modified destructively).

author

- Gergö Barany <gergo@tud.at>

license

- LGPL

 empty_p_hashtbl(-Table) is det

Unifies Table with a newly created empty hash table of a default size.

 empty_p_hashtbl(-Table, +Size) is det

Unifies Table with a newly created empty hash table with the number of buckets given by Size.

throws

- Type or domain error if Size is not a non-negative integer.

 p_hashtbl_put(+Table, +Key, +Value, -TableOut) is det

TableOut is a hash table like Table, except that in TableOut Key is mapped to Value. If Key is already mapped to some values in Table, those mappings are present but shadowed by Value in TableOut.

 p_hashtbl_set(+Table, +Key, +Value, -TableOut) is det

TableOut is a hash table like Table, except that in TableOut Key is mapped to Value. If Key is already mapped to some values in Table, the most recent one of those is replaced by Value. Other values for Key remain shadowed in TableOut.

 p_hashtbl_get(+Table, +Key, -Value) is semidet

Gets the most recently stored Value for Key in Table, if any. Fails if no values are stored for Key. There is no separate predicate for membership checks, use p_hashtbl_get(Table, Key, _) to test whether Key is present in Table.

 p_hashtbl_get_all(+Table, +Key, -Value) is nondet

On backtracking, enumerates every Value associated with Key in Table. Fails if no values are stored for Key. The order of enumeration is the most recently added value for Key first (the same as the solution for p_hashtbl_get/3), then shadowed ones.

 p_hashtbl_get_default(+Table, +Key, ?Default, -Value, -TableOut) is det

If Table contains an entry for Key, unifies Value with the corresponding value as in p_hashtbl_get/3 and TableOut with Table. Otherwise, unifies Value with Default and adds this value to the Table under Key (as by p_hashtbl_put/4) and unifies TableOut with the resulting table.

 p_hashtbl_delete(!Table, +Key, -TableOut) is det

Deletes the most recent value stored under Key in Table, if any. Does nothing otherwise; succeeds always.

 p_hashtbl_enumerate(+Table, -Key, -Value) is nondet

On backtracking, enumerates every Key-Value pair stored in the Table. Fails if the table is empty. If several values are stored for the same key, their order of enumeration is most recent first, as in p_hashtbl_get_all/3. The ordering is otherwise unspecified.

If Key is ground, this behaves like p_hashtbl_get_all/3 for that Key. However, p_hashtbl_get_all/3 is more efficient in this case.

 p_hashtbl_to_list(+Table, -Pairs) is det

Unifies Pairs with a list of all Key-Value pairs in the order as enumerated by p_hashtbl_enumerate/3.

 list_to_p_hashtbl(+Pairs, -Table) is semidet

If Pairs is a list of Key-Value pairs, unifies Table with a corresponding hash table of a default size containing all those pairs. If there are several entries for the same Key in the list, later entries will shadow earlier ones in the Table.

 list_to_p_hashtbl(+Pairs, -Table, +Size) is semidet

As list_to_p_hashtbl/2, but the hash table has an initial number of buckets given by Size.

throws

- Type or domain error if Size is not a non-negative integer.

 p_hashtbl_map(+Table, :Goal, -TableOut) is nondet

For every Key and Value in Table, calls Goal(Key, Value, Value1) and unifies TableOut with a hash table containing all Key-Value1 pairs. Deterministic if Goal is deterministic. If Goal backtracks, p_hashtbl_map/3 enumerates several TableOut tables accordingly.

 p_hashtbl_fold(+Table, :Goal, +Acc, -Result) is nondet

Folds Goal over every Key and Value in the Table. Calls Goal(Key, Value, Acc, Result), using each call's Result as the next call's accumulator Acc, and unifying Result with the final call's Result. Deterministic if Goal is deterministic. If Goal backtracks, enumerates several results accordingly.

 p_hashtbl_iter(+Table, :Goal) is nondet

Calls Goal(Key, Value) for every Key and Value stored in Table. This is useful to ensure that all entries satisfy some predicate, or for Goal's side effects. Deterministic if Goal is deterministic.

 p_hashtbl_unfold(:Goal, -Table) is det

Unfolds the binary goal Goal into the Table: Unifies Table with a hash table containing a Key-Value entry for every solution of Goal(Key, Value). Table is empty if Goal has no solutions. Later solutions of Goal will shadow earlier ones in Table.