/usr/share/octave/packages/interval-2.1.0/@infsupdec/mpower.m is in octave-interval 2.1.0-2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 | ## Copyright 2016 Oliver Heimlich
##
## 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
## @defop Method {@@infsup} mpower (@var{X}, @var{Y})
## @defopx Operator {@@infsup} {@var{X} ^ @var{Y}}
##
## Return the matrix power operation of @var{X} raised to the @var{Y} power.
##
## If @var{X} is a scalar, this function and @code{power} are equivalent.
## Otherwise, @var{X} must be a square matrix and @var{Y} must be a single
## integer.
##
## Warning: This function is not defined by IEEE Std 1788-2015.
##
## Accuracy: The result is a valid enclosure. The result is tightest for
## @var{Y} in @{0, 1, 2@}.
##
## @example
## @group
## infsupdec (magic (3)) ^ 2
## @result{} ans = 3×3 interval matrix
## [91]_com [67]_com [67]_com
## [67]_com [91]_com [67]_com
## [67]_com [67]_com [91]_com
## @end group
## @end example
## @seealso{@@infsupdec/pow, @@infsupdec/pown, @@infsupdec/pow2, @@infsupdec/pow10, @@infsupdec/exp}
## @end defop
## Author: Oliver Heimlich
## Keywords: interval
## Created: 2016-01-24
function result = mpower (x, y)
if (nargin != 2)
print_usage ();
return
endif
if (not (isa (x, "infsupdec")))
x = infsupdec (x);
endif
if (isscalar (x.dec))
## Short-circuit for scalars
result = power (x, y);
return
endif
if (not (isreal (y)) || fix (y) ~= y)
error ("interval:InvalidOperand", ...
"mpower: only integral powers can be computed");
endif
result = newdec (mpower (x.infsup, y));
if (y < 0)
result.dec(:) = _trv ();
elseif (y < 2)
result.dec = x.dec;
elseif (y == 2)
warning ('off', 'Octave:broadcast', 'local');
result.dec = min (result.dec, min (min (x.dec, [], 1), ...
min (x.dec, [], 2)));
elseif (y > 2)
result.dec = min (result.dec, min (vec (x.dec)));
endif
endfunction
%!# from the documentation string
%!assert (isequal (infsupdec (magic (3)) ^ 2, infsupdec (magic (3) ^ 2)));
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