/
counters.lgt
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/
counters.lgt
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% This file is part of Logtalk <https://logtalk.org/>
% SPDX-FileCopyrightText: 1998-2023 Paulo Moura <pmoura@logtalk.org>
% SPDX-License-Identifier: Apache-2.0
%
% Licensed under the Apache License, Version 2.0 (the "License");
% you may not use this file except in compliance with the License.
% You may obtain a copy of the License at
%
% http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS,
% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
% See the License for the specific language governing permissions and
% limitations under the License.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
:- object(counters).
:- public([
counter/2,
inc_counter/1,
dec_counter/1,
save_counters/0
]).
:- private(counter_value_/2).
:- dynamic(counter_value_/2).
% load the counters persistent database file when the object is compiled and loaded
:- include('counters.pl').
counter(Counter, Value) :-
counter_value_(Counter, Value).
inc_counter(Counter) :-
retract(counter_value_(Counter, Old)),
New is Old + 1,
assertz(counter_value_(Counter, New)).
dec_counter(Counter) :-
retract(counter_value_(Counter, Old)),
New is Old - 1,
assertz(counter_value_(Counter, New)).
save_counters :-
% save the current state of the counters database to a persistent file
logtalk::expand_library_path(includes, Directory),
atom_concat(Directory, 'counters.pl', Path),
open(Path, write, Stream),
( counter_value_(Counter, Value),
write_canonical(Stream, counter_value_(Counter,Value)), write(Stream, '.\n'),
fail
; true
),
close(Stream).
:- end_object.