/usr/share/octave/packages/interval-2.1.0/@infsup/log10.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 {@@infsup} log10 (@var{X})
##
## Compute the decimal (base-10) logarithm.
##
## The function is only defined where @var{X} is positive.
##
## Accuracy: The result is a tight enclosure.
##
## @example
## @group
## log10 (infsup (2))
## @result{} ans ⊂ [0.30102, 0.30103]
## @end group
## @end example
## @seealso{@@infsup/pow10, @@infsup/log, @@infsup/log2}
## @end defmethod
## Author: Oliver Heimlich
## Keywords: interval
## Created: 2014-10-04
function x = log10 (x)
if (nargin ~= 1)
print_usage ();
return
endif
x = intersect (x, infsup (0, inf));
## log10 is monotonically increasing from (0, -inf) to (inf, inf)
if (__check_crlibm__ ())
l = crlibm_function ('log10', -inf, x.inf); # this works for empty intervals
u = crlibm_function ('log10', +inf, x.sup); # ... this does not
else
l = mpfr_function_d ('log10', -inf, x.inf); # this works for empty intervals
u = mpfr_function_d ('log10', +inf, x.sup); # ... this does not
endif
l(x.sup == 0) = inf;
l(l == 0) = -0;
u(isempty (x) | x.sup == 0) = -inf;
x.inf = l;
x.sup = u;
endfunction
%!# from the documentation string
%!assert (log10 (infsup (2)) == "[0x1.34413509F79FEp-2, 0x1.34413509F79FFp-2]");
%!# correct use of signed zeros
%!test
%! x = log10 (infsup (1));
%! assert (signbit (inf (x)));
%! assert (not (signbit (sup (x))));
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