function o = uminus(o)

% Overloads the unary minus operator for dates objects. Shifts all the elements by one period.
%
% INPUTS
% - o [dates]
%
% OUTPUTS
% - o [dates]

% Copyright © 2013-2023 Dynare Team
%
% This code is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% Dynare dates submodule is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with Dynare.  If not, see <https://www.gnu.org/licenses/>.

o.time(:) = o.time(:)-1;

return % --*-- Unit tests --*--

%@test:1
% Define some dates
date_1 = '1950Y';
date_2 = '1950Q2';
date_3 = '1950Q1';
date_4 = '1950M2';
date_5 = '1950M1';

% Call the tested routine.
try
    d1 = dates(date_1); -d1;
    d2 = dates(date_2); -d2;
    d3 = dates(date_3); -d3;
    d4 = dates(date_4); -d4;
    d5 = dates(date_5); -d5;
    t(1) = true;
catch
    t(1) = false;
end

if t(1)
    t(2) = (d1==dates('1949Y'));
    t(3) = (d2==dates('1950Q1'));
    t(4) = (d3==dates('1949Q4'));
    t(5) = (d4==dates('1950M1'));
    t(6) = (d5==dates('1949M12'));
end
T = all(t);
%@eof:1

%@test:2
d1 = dates('1950Q1','1950Q2','1950Q3','1950Q4','1951Q1');
d2 = dates('1949Q4','1950Q1','1950Q2','1950Q3','1950Q4');
try
  -d1;
  t(1) = true;
catch
  t(1) = false;
end

if t(1)
  t(2) = isequal(d2, d1);
end

T = all(t);
%@eof:2

%@test:3
d1 = dates('2000-01-01');
d2 = dates('1999-12-31');
try
  -d1;
  t(1) = true;
catch
  t(1) = false;
end

if t(1)
  t(2) = (d2==d1);
end

T = all(t);
%@eof:3
