/usr/share/octave/packages/interval-2.1.0/@infsupdec/abs.m is in octave-interval 2.1.0-2.
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##
## This program 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.
##
## This program 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 this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @documentencoding UTF-8
## @defmethod {@@infsupdec} abs (@var{X})
##
## Compute the absolute value of numbers.
##
## Accuracy: The result is a tight enclosure.
##
## @example
## @group
## abs (infsupdec (2.5, 3.5))
## @result{} ans = [2.5, 3.5]_com
## abs (infsupdec (-0.5, 5.5))
## @result{} ans = [0, 5.5]_com
## @end group
## @end example
## @seealso{@@infsupdec/mag, @@infsupdec/mig}
## @end defmethod
## Author: Oliver Heimlich
## Keywords: interval
## Created: 2014-10-13
function result = abs (x)
if (nargin ~= 1)
print_usage ();
return
endif
result = newdec (abs (x.infsup));
## abs is defined and continuous everywhere
result.dec = min (result.dec, x.dec);
endfunction
%!# Empty interval
%!assert (isequal (abs (infsupdec ()), infsupdec ()));
%!# Singleton intervals
%!assert (isequal (abs (infsupdec (1)), infsupdec (1)));
%!assert (isequal (abs (infsupdec (0)), infsupdec (0)));
%!assert (isequal (abs (infsupdec (-1)), infsupdec (1)));
%!assert (isequal (abs (infsupdec (realmax)), infsupdec (realmax)));
%!assert (isequal (abs (infsupdec (realmin)), infsupdec (realmin)));
%!assert (isequal (abs (infsupdec (-realmin)), infsupdec (realmin)));
%!assert (isequal (abs (infsupdec (-realmax)), infsupdec (realmax)));
%!# Bounded intervals
%!assert (isequal (abs (infsupdec (1, 2)), infsupdec (1, 2)));
%!assert (isequal (abs (infsupdec (0, 1)), infsupdec (0, 1)));
%!assert (isequal (abs (infsupdec (-1, 1)), infsupdec (0, 1)));
%!assert (isequal (abs (infsupdec (-1, 0)), infsupdec (0, 1)));
%!assert (isequal (abs (infsupdec (-2, -1)), infsupdec (1, 2)));
%!# Unbounded intervals
%!assert (isequal (abs (infsupdec (0, inf)), infsupdec (0, inf)));
%!assert (isequal (abs (infsupdec (-inf, inf)), infsupdec (0, inf)));
%!assert (isequal (abs (infsupdec (-inf, 0)), infsupdec (0, inf)));
%!assert (isequal (abs (infsupdec (1, inf)), infsupdec (1, inf)));
%!assert (isequal (abs (infsupdec (-1, inf)), infsupdec (0, inf)));
%!assert (isequal (abs (infsupdec (-inf, -1)), infsupdec (1, inf)));
%!assert (isequal (abs (infsupdec (-inf, 1)), infsupdec (0, inf)));
%!# from the documentation string
%!assert (isequal (abs (infsupdec (2.5, 3.5)), infsupdec (2.5, 3.5)));
%!assert (isequal (abs (infsupdec (-0.5, 5.5)), infsupdec (0, 5.5)));
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