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% vim: ts=4 sw=4 et ft=mercury
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% Copyright (C) 1994-1995,1997,1999,2004-2006,2008,2011-2012 The University of Melbourne.
% Copyright (C) 2013-2018 The Mercury team.
% This file is distributed under the terms specified in COPYING.LIB.
%--------------------------------------------------%
%
% File: bimap.m.
% Main author: conway.
% Stability: medium.
%
% This file provides a bijective map ADT.
% A map (also known as a dictionary or an associative array) is a collection
% of (Key, Data) pairs which allows you to look up any Data item given the
% Key. A bimap also allows you to efficiently look up the Key given the Data.
% This time efficiency comes at the expense of using twice as much space.
%
%--------------------------------------------------%
%--------------------------------------------------%

:- module bimap.
:- interface.

:- import_module assoc_list.
:- import_module list.
:- import_module map.
:- import_module maybe.

%--------------------------------------------------%

:- type bimap(K, V).

%--------------------------------------------------%

    % Initialize an empty bimap.
    %
:- func init = bimap(K, V).
:- pred init(bimap(K, V)::out) is det.

    % Initialize a bimap with the given key-value pair.
    %
:- func singleton(K, V) = bimap(K, V).

    % Check whether a bimap is empty.
    %
:- pred is_empty(bimap(K, V)::in) is semidet.

    % True if both bimaps have the same set of key-value pairs, regardless of
    % how the bimaps were constructed.
    %
    % Unifying bimaps does not work as one might expect because the internal
    % structures of two bimaps that contain the same set of key-value pairs
    % may be different.
    %
:- pred equal(bimap(K, V)::in, bimap(K, V)::in) is semidet.

    % Search the bimap. The first mode searches for a value given a key
    % and the second mode searches for a key given a value.
    %
:- pred search(bimap(K, V), K, V).
:- mode search(in, in, out) is semidet.
:- mode search(in, out, in) is semidet.

    % Search the bimap for the value corresponding to a given key.
    %
:- func forward_search(bimap(K, V), K) = V is semidet.
:- pred forward_search(bimap(K, V)::in, K::in, V::out) is semidet.

    % Search the bimap for the key corresponding to the given value.
    %
:- func reverse_search(bimap(K, V), V) = K is semidet.
:- pred reverse_search(bimap(K, V)::in, K::out, V::in) is semidet.

    % Look up the value in the bimap corresponding to the given key.
    % Throws an exception if the key is not present in the bimap.
    %
:- func lookup(bimap(K, V), K) = V.
:- pred lookup(bimap(K, V)::in, K::in, V::out) is det.

    % Look up the key in the bimap corresponding to the given value.
    % Throws an exception if the value is not present in the bimap.
    %
:- func reverse_lookup(bimap(K, V), V) = K.
:- pred reverse_lookup(bimap(K, V)::in, K::out, V::in) is det.

    % Succeeds iff the bimap contains the given key.
    %
:- pred contains_key(bimap(K, V)::in, K::in) is semidet.

    % Succeeds iff the bimap contains the given value.
    %
:- pred contains_value(bimap(K, V)::in, V::in) is semidet.

    % Given a bimap, return a list of all the keys in the bimap.
    %
:- func ordinates(bimap(K, V)) = list(K).
:- pred ordinates(bimap(K, V)::in, list(K)::out) is det.

    % Given a bimap, return a list of all the data values in the bimap.
    %
:- func coordinates(bimap(K, V)) = list(V).
:- pred coordinates(bimap(K, V)::in, list(V)::out) is det.

    % Insert a new key-value pair into the bimap.
    % Fails if either the key or value already exists.
    %
:- func insert(bimap(K, V), K, V) = bimap(K, V) is semidet.
:- pred insert(K::in, V::in, bimap(K, V)::in, bimap(K, V)::out)
    is semidet.

    % As above but throws an exception if the key or value already
    % exists.
    %
:- func det_insert(bimap(K, V), K, V) = bimap(K, V).
:- pred det_insert(K::in, V::in, bimap(K, V)::in, bimap(K, V)::out)
    is det.

    % search_insert(K, V, MaybeOldV, !Bimap):
    %
    % Search for the key K in the bimap. If the key is already in the bimap,
    % with corresponding value OldV, set MaybeOldV to yes(OldV). If it
    % is not in the bimap, then insert it with value V, and set MaybeOldV
    % to no. The value of V should be guaranteed to be different to
    % all the values already in !.Bimap. If it isn't, this predicate
    % will throw an exception.
    %
:- pred search_insert(K::in, V::in, maybe(V)::out,
    bimap(K, V)::in, bimap(K, V)::out) is det.

    % Update the key and value if already present, otherwise insert the
    % new key and value.
    %
    % NOTE: setting the key-value pair (K, V) will remove the key-value pairs
    % (K, V1) and (K1, V) if they exist.
    %
:- func set(bimap(K, V), K, V) = bimap(K, V).
:- pred set(K::in, V::in, bimap(K, V)::in, bimap(K, V)::out) is det.

    % Insert key-value pairs from an association list into the given bimap.
    % Fails if the contents of the association list and the initial bimap
    % do not implicitly form a bijection.
    %
:- func insert_from_assoc_list(assoc_list(K, V), bimap(K, V)) =
    bimap(K, V) is semidet.
:- pred insert_from_assoc_list(assoc_list(K, V)::in,
    bimap(K, V)::in, bimap(K, V)::out) is semidet.

    % As above but throws an exception if the association list and
    % initial bimap are not implicitly bijective.
    %
:- func det_insert_from_assoc_list(assoc_list(K, V), bimap(K, V))
    = bimap(K, V).
:- pred det_insert_from_assoc_list(assoc_list(K, V)::in,
    bimap(K, V)::in, bimap(K, V)::out) is det.

    % Insert key-value pairs from a pair of corresponding lists.
    % Throws an exception if the lists are not of equal lengths
    % or if they do not implicitly define a bijection.
    %
:- func det_insert_from_corresponding_lists(list(K), list(V),
    bimap(K, V)) = bimap(K, V).
:- pred det_insert_from_corresponding_lists(list(K)::in, list(V)::in,
    bimap(K, V)::in, bimap(K, V)::out) is det.

    % Apply set to each key-value pair in the association list.
    % The key-value pairs from the association list may update existing keys
    % and values in the bimap.
    %
:- func set_from_assoc_list(assoc_list(K, V), bimap(K, V))
    = bimap(K, V).
:- pred set_from_assoc_list(assoc_list(K, V)::in,
    bimap(K, V)::in, bimap(K, V)::out) is det.

    % As above but with a pair of corresponding lists in place of an
    % association list. Throws an exception if the lists are not of
    % equal length.
    %
:- func set_from_corresponding_lists(list(K), list(V),
    bimap(K, V)) = bimap(K, V).
:- pred set_from_corresponding_lists(list(K)::in, list(V)::in,
    bimap(K, V)::in, bimap(K, V)::out) is det.

    % Delete a key-value pair from a bimap. If the key is not present,
    % leave the bimap unchanged.
    %
:- func delete_key(bimap(K, V), K) = bimap(K, V).
:- pred delete_key(K::in, bimap(K, V)::in, bimap(K, V)::out) is det.

    % Delete a key-value pair from a bimap. If the value is not present,
    % leave the bimap unchanged.
    %
:- func delete_value(bimap(K, V), V) = bimap(K, V).
:- pred delete_value(V::in, bimap(K, V)::in, bimap(K, V)::out) is det.

    % Apply delete_key to a list of keys.
    %
:- func delete_keys(bimap(K, V), list(K)) = bimap(K, V).
:- pred delete_keys(list(K)::in, bimap(K, V)::in, bimap(K, V)::out)
    is det.

    % Apply delete_value to a list of values.
    %
:- func delete_values(bimap(K, V), list(V)) = bimap(K, V).
:- pred delete_values(list(V)::in, bimap(K, V)::in, bimap(K, V)::out)
    is det.

    % overlay(BIMapA, BIMapB, BIMap):
    % Apply map.overlay to the forward maps of BIMapA and BIMapB,
    % and compute the reverse map from the resulting map.
    %
:- func overlay(bimap(K, V), bimap(K, V)) = bimap(K, V).
:- pred overlay(bimap(K, V)::in, bimap(K, V)::in, bimap(K, V)::out)
    is det.

    % Count the number of key-value pairs in the bimap.
    %
:- func count(bimap(K, V)) = int.

    % Convert a bimap to an association list.
    %
:- func to_assoc_list(bimap(K, V)) = assoc_list(K, V).
:- pred to_assoc_list(bimap(K, V)::in, assoc_list(K, V)::out) is det.

    % Convert an association list to a bimap. Fails if the association list
    % does not implicitly define a bijection, i.e. a key or value occurs
    % multiple times in the association list.
    %
:- func from_assoc_list(assoc_list(K, V)) = bimap(K, V) is semidet.
:- pred from_assoc_list(assoc_list(K, V)::in, bimap(K, V)::out)
    is semidet.

    % As above but throws an exception instead of failing if the
    % association list does not implicitly define a bijection.
    %
:- func det_from_assoc_list(assoc_list(K, V)) = bimap(K, V).
:- pred det_from_assoc_list(assoc_list(K, V)::in, bimap(K, V)::out)
    is det.

    % Convert a pair of lists into a bimap. Fails if the lists do not
    % implicitly define a bijection or if the lists are of unequal length.
    %
:- func from_corresponding_lists(list(K), list(V)) = bimap(K, V)
    is semidet.
:- pred from_corresponding_lists(list(K)::in, list(V)::in,
    bimap(K, V)::out) is semidet.

    % As above but throws an exception instead of failing if the lists
    % do not implicitly define a bijection or are of unequal length.
    %
:- func det_from_corresponding_lists(list(K), list(V)) = bimap(K, V).
:- pred det_from_corresponding_lists(list(K)::in, list(V)::in,
    bimap(K, V)::out) is det.

:- func apply_forward_map_to_list(bimap(K, V), list(K)) = list(V).
:- pred apply_forward_map_to_list(bimap(K, V)::in, list(K)::in,
    list(V)::out) is det.

:- func apply_reverse_map_to_list(bimap(K, V), list(V)) = list(K).
:- pred apply_reverse_map_to_list(bimap(K, V)::in, list(V)::in,
    list(K)::out) is det.

    % Apply a transformation predicate to all the keys.
    % Throws an exception if the resulting bimap is not bijective.
    %
:- func map_keys(func(V, K) = L, bimap(K, V)) = bimap(L, V).
:- pred map_keys(pred(V, K, L)::in(pred(in, in, out) is det),
    bimap(K, V)::in, bimap(L, V)::out) is det.

    % Apply a transformation predicate to all the values.
    % Throws an exception if the resulting bimap is not bijective.
    %
:- func map_values(func(K, V) = W, bimap(K, V)) = bimap(K, W).
:- pred map_values(pred(K, V, W)::in(pred(in, in, out) is det),
    bimap(K, V)::in, bimap(K, W)::out) is det.

    % Perform an inorder traversal, by key, of the bimap, applying an
    % accumulator predicate for each key-value pair.
    %
:- func foldl(func(K, V, A) = A, bimap(K, V), A) = A.
:- pred foldl(pred(K, V, A, A), bimap(K, V), A, A).
:- mode foldl(pred(in, in, in, out) is det, in, in, out) is det.
:- mode foldl(pred(in, in, mdi, muo) is det, in, mdi, muo) is det.
:- mode foldl(pred(in, in, di, uo) is det, in, di, uo) is det.
:- mode foldl(pred(in, in, in, out) is semidet, in, in, out) is semidet.
:- mode foldl(pred(in, in, mdi, muo) is semidet, in, mdi, muo) is semidet.
:- mode foldl(pred(in, in, di, uo) is semidet, in, di, uo) is semidet.

    % Perform a traversal of the bimap, applying an accumulator predicate
    % with two accumulators for each key-value pair. (Although no more
    % expressive than foldl, this is often a more convenient format,
    % and a little more efficient).
    %
:- pred foldl2(pred(K, V, A, A, B, B), bimap(K, V), A, A, B, B).
:- mode foldl2(pred(in, in, in, out, in, out) is det,
    in, in, out, in, out) is det.
:- mode foldl2(pred(in, in, in, out, mdi, muo) is det,
    in, in, out, mdi, muo) is det.
:- mode foldl2(pred(in, in, in, out, di, uo) is det,
    in, in, out, di, uo) is det.
:- mode foldl2(pred(in, in, di, uo, di, uo) is det,
    in, di, uo, di, uo) is det.
:- mode foldl2(pred(in, in, in, out, in, out) is semidet,
    in, in, out, in, out) is semidet.
:- mode foldl2(pred(in, in, in, out, mdi, muo) is semidet,
    in, in, out, mdi, muo) is semidet.
:- mode foldl2(pred(in, in, in, out, di, uo) is semidet,
    in, in, out, di, uo) is semidet.

    % Perform a traversal of the bimap, applying an accumulator predicate
    % with three accumulators for each key-value pair. (Although no more
    % expressive than foldl, this is often a more convenient format,
    % and a little more efficient).
    %
:- pred foldl3(pred(K, V, A, A, B, B, C, C), bimap(K, V),
    A, A, B, B, C, C).
:- mode foldl3(pred(in, in, in, out, in, out, in, out) is det,
    in, in, out, in, out, in, out) is det.
:- mode foldl3(pred(in, in, in, out, in, out, mdi, muo) is det,
    in, in, out, in, out, mdi, muo) is det.
:- mode foldl3(pred(in, in, in, out, in, out, di, uo) is det,
    in, in, out, in, out, di, uo) is det.
:- mode foldl3(pred(in, in, in, out, di, uo, di, uo) is det,
    in, in, out, di, uo, di, uo) is det.
:- mode foldl3(pred(in, in, di, uo, di, uo, di, uo) is det,
    in, di, uo, di, uo, di, uo) is det.
:- mode foldl3(pred(in, in, in, out, in, out, in, out) is semidet,
    in, in, out, in, out, in, out) is semidet.
:- mode foldl3(pred(in, in, in, out, in, out, mdi, muo) is semidet,
    in, in, out, in, out, mdi, muo) is semidet.
:- mode foldl3(pred(in, in, in, out, in, out, di, uo) is semidet,
    in, in, out, in, out, di, uo) is semidet.

    % Extract a the forward map from the bimap, the map from key to value.
    %
:- func forward_map(bimap(K, V)) = map(K, V).

    % Extract the reverse map from the bimap, the map from value to key.
    %
:- func reverse_map(bimap(K, V)) = map(V, K).

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