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% vim: ft=mercury ts=4 sw=4 et
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% Copyright (C) 1995-1997, 1999-2001, 2004-2006, 2010-2011 The University of Melbourne.
% Copyright (C) 2013-2018 The Mercury team.
% This file is distributed under the terms specified in COPYING.LIB.
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%
% File: assoc_list.m.
% Main authors: fjh, zs.
% Stability: medium to high.
%
% This file contains the definition of the type assoc_list(K, V)
% and some predicates which operate on those types.
%
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:- module assoc_list.
:- interface.

:- import_module list.
:- import_module pair.

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

:- type assoc_list(K, V) == list(pair(K, V)).

:- type assoc_list(T) == list(pair(T, T)).

    % Swap the two sides of the pairs in each member of the list.
    %
:- func reverse_members(assoc_list(K, V)) = assoc_list(V, K).
:- pred reverse_members(assoc_list(K, V)::in, assoc_list(V, K)::out) is det.

    % Zip together two lists.
    % Throw an exception if they are of different lengths.
    %
:- func from_corresponding_lists(list(K), list(V)) = assoc_list(K, V).
:- pred from_corresponding_lists(list(K)::in, list(V)::in,
    assoc_list(K, V)::out) is det.

    % Return the first member of each pair.
    %
:- func keys(assoc_list(K, V)) = list(K).
:- pred keys(assoc_list(K, V)::in, list(K)::out) is det.

    % Return the second member of each pair.
    %
:- func values(assoc_list(K, V)) = list(V).
:- pred values(assoc_list(K, V)::in, list(V)::out) is det.

    % Return two lists containing respectively the first and the second member
    % of each pair in the assoc_list.
    %
:- pred keys_and_values(assoc_list(K, V)::in,
    list(K)::out, list(V)::out) is det.

    % Find the first element of the association list that matches
    % the given key, and return the associated value.
    %
:- pred search(assoc_list(K, V)::in, K::in, V::out) is semidet.

    % An alternative version of search.
    %
:- func assoc_list(K, V) ^ elem(K) = V is semidet.

    % An alternative version of search that throws an exception if the key in
    % question does not appear in the assoc_list.
    %
:- func assoc_list(K, V) ^ det_elem(K) = V is det.

    % Find the first element of the association list that matches the given
    % key. Return the associated value, and the original list with the selected
    % element removed.
    %
:- pred remove(assoc_list(K, V)::in, K::in, V::out, assoc_list(K, V)::out)
    is semidet.

    % As above, but with an argument ordering that is more conducive to
    % the use of state variable notation.
    %
:- pred svremove(K::in, V::out, assoc_list(K, V)::in, assoc_list(K, V)::out)
    is semidet.

:- func map_keys_only(func(K) = L, assoc_list(K, V)) = assoc_list(L, V).
:- pred map_keys_only(pred(K, L), assoc_list(K, V), assoc_list(L, V)).
:- mode map_keys_only(pred(in, out) is det, in, out) is det.

:- func map_values_only(func(V) = W, assoc_list(K, V)) = assoc_list(K, W).
:- pred map_values_only(pred(V, W), assoc_list(K, V), assoc_list(K, W)).
:- mode map_values_only(pred(in, out) is det, in, out) is det.

:- func map_values(func(K, V) = W, assoc_list(K, V)) = assoc_list(K, W).
:- pred map_values(pred(K, V, W), assoc_list(K, V), assoc_list(K, W)).
:- mode map_values(pred(in, in, out) is det, in, out) is det.

    % filter(Pred, List, TrueList) takes a closure with one
    % input argument and for each member K - V of List X, calls the closure
    % on the key. K - V is included in TrueList iff Pred(K) is true.
    %
:- pred filter(pred(K)::in(pred(in) is semidet),
    assoc_list(K, V)::in, assoc_list(K, V)::out) is det.
:- func filter(pred(K)::in(pred(in) is semidet),
    assoc_list(K, V)::in) = (assoc_list(K, V)::out) is det.

    % negated_filter(Pred, List, FalseList) takes a closure with one
    % input argument and for each member K - V of List X, calls the closure
    % on the key. K - V is included in FalseList iff Pred(K) is false.
    %
:- pred negated_filter(pred(K)::in(pred(in) is semidet),
    assoc_list(K, V)::in, assoc_list(K, V)::out) is det.
:- func negated_filter(pred(K)::in(pred(in) is semidet),
    assoc_list(K, V)::in) = (assoc_list(K, V)::out) is det.

    % filter(Pred, List, TrueList, FalseList) takes a closure with
    % one input argument and for each member K - V of List X, calls the closure
    % on the key. K - V is included in TrueList iff Pred(K) is true.
    % K - V is included in FalseList iff Pred(K) is false.
    %
:- pred filter(pred(K)::in(pred(in) is semidet),
    assoc_list(K, V)::in, assoc_list(K, V)::out, assoc_list(K, V)::out) is det.

    % merge(L1, L2, L):
    %
    % L is the result of merging the elements of L1 and L2, in ascending order.
    % L1 and L2 must be sorted on the keys.
    %
:- func merge(assoc_list(K, V), assoc_list(K, V)) = assoc_list(K, V).
:- pred merge(assoc_list(K, V)::in, assoc_list(K, V)::in,
    assoc_list(K, V)::out) is det.

    % foldl_keys(Pred, List, Start End) calls Pred
    % with each key in List (working left-to-right) and an accumulator
    % (with initial value of Start), and returns the final value in End.
    %
:- pred foldl_keys(pred(K, A, A), assoc_list(K, V), A, A).
:- mode foldl_keys(pred(in, in, out) is det, in, in, out) is det.
:- mode foldl_keys(pred(in, mdi, muo) is det, in, mdi, muo) is det.
:- mode foldl_keys(pred(in, di, uo) is det, in, di, uo) is det.
:- mode foldl_keys(pred(in, in, out) is semidet, in, in, out) is semidet.
:- mode foldl_keys(pred(in, mdi, muo) is semidet, in, mdi, muo) is semidet.
:- mode foldl_keys(pred(in, di, uo) is semidet, in, di, uo) is semidet.
:- mode foldl_keys(pred(in, in, out) is multi, in, in, out) is multi.
:- mode foldl_keys(pred(in, in, out) is nondet, in, in, out) is nondet.

    % foldl_values(Pred, List, Start End) calls Pred
    % with each value in List (working left-to-right) and an accumulator
    % (with initial value of Start), and returns the final value in End.
    %
:- pred foldl_values(pred(V, A, A), assoc_list(K, V), A, A).
:- mode foldl_values(pred(in, in, out) is det, in,
    in, out) is det.
:- mode foldl_values(pred(in, mdi, muo) is det, in,
    mdi, muo) is det.
:- mode foldl_values(pred(in, di, uo) is det, in,
    di, uo) is det.
:- mode foldl_values(pred(in, in, out) is semidet, in,
    in, out) is semidet.
:- mode foldl_values(pred(in, mdi, muo) is semidet, in,
    mdi, muo) is semidet.
:- mode foldl_values(pred(in, di, uo) is semidet, in,
    di, uo) is semidet.
:- mode foldl_values(pred(in, in, out) is multi, in,
    in, out) is multi.
:- mode foldl_values(pred(in, in, out) is nondet, in,
    in, out) is nondet.

    % As above, but with two accumulators.
    %
:- pred foldl2_values(pred(V, A, A, B, B), assoc_list(K, V),
    A, A, B, B).
:- mode foldl2_values(pred(in, in, out, in, out) is det, in,
    in, out, in, out) is det.
:- mode foldl2_values(pred(in, in, out, mdi, muo) is det, in,
    in, out, mdi, muo) is det.
:- mode foldl2_values(pred(in, in, out, di, uo) is det, in,
    in, out, di, uo) is det.
:- mode foldl2_values(pred(in, in, out, in, out) is semidet, in,
    in, out, in, out) is semidet.
:- mode foldl2_values(pred(in, in, out, mdi, muo) is semidet, in,
    in, out, mdi, muo) is semidet.
:- mode foldl2_values(pred(in, in, out, di, uo) is semidet, in,
    in, out, di, uo) is semidet.
:- mode foldl2_values(pred(in, in, out, in, out) is multi, in,
    in, out, in, out) is multi.
:- mode foldl2_values(pred(in, in, out, in, out) is nondet, in,
    in, out, in, out) is nondet.

    % As above, but with three accumulators.
    %
:- pred foldl3_values(pred(V, A, A, B, B, C, C), assoc_list(K, V),
    A, A, B, B, C, C).
:- mode foldl3_values(pred(in, in, out, in, out, in, out) is det,
    in, in, out, in, out, in, out) is det.
:- mode foldl3_values(pred(in, in, out, in, out, mdi, muo) is det,
    in, in, out, in, out, mdi, muo) is det.
:- mode foldl3_values(pred(in, in, out, in, out, di, uo) is det,
    in, in, out, in, out, di, uo) is det.
:- mode foldl3_values(pred(in, in, out, in, out, in, out) is semidet,
    in, in, out, in, out, in, out) is semidet.
:- mode foldl3_values(pred(in, in, out, in, out, mdi, muo) is semidet,
    in, in, out, in, out, mdi, muo) is semidet.
:- mode foldl3_values(pred(in, in, out, in, out, di, uo) is semidet,
    in, in, out, in, out, di, uo) is semidet.
:- mode foldl3_values(pred(in, in, out, in, out, in, out) is multi,
    in, in, out, in, out, in, out) is multi.
:- mode foldl3_values(pred(in, in, out, in, out, in, out) is nondet,
    in, in, out, in, out, in, out) is nondet.

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