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########################################################################
##
## Copyright (C) 1996-2022 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave 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.
##
## Octave 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 Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {@var{hstr} =} dec2hex (@var{d})
## @deftypefnx {} {@var{hstr} =} dec2hex (@var{d}, @var{len})
## Return a string representing the conversion of the integer @var{d} to a
## hexadecimal (base16) number.
##
## If @var{d} is negative, return the hexadecimal equivalent of the two's
## complement binary value of @var{d}.
## If @var{d} is a matrix or cell array, return a string matrix with one row
## for each element in @var{d}, padded with leading zeros to the width of the
## largest value.
##
## The optional second argument, @var{len}, specifies the minimum number of
## digits in the result.
##
## Examples:
##
## @example
## @group
## dec2hex (2748)
## @result{} "ABC"
##
## dec2hex (-2)
## @result{} "FE"
## @end group
## @end example
##
## @seealso{hex2dec, dec2base, dec2bin}
## @end deftypefn
function hstr = dec2hex (d, len)
if (nargin == 0)
print_usage ();
endif
## To avoid repeating a lot of code, including input validation, we call dec2bin.
if (nargin == 2)
d = dec2bin (d, len*4);
else
d = dec2bin (d);
endif
## Left-pad with zeros to make the number of columns divisible by 4
n = mod (columns (d), 4);
if (n > 0)
d = [repmat("0", rows(d), 4-n), d];
endif
d -= "0"; # convert to numeric
d = d(:, 1:4:end) * 8 + d(:, 2:4:end) * 4 + d(:, 3:4:end) * 2 + d(:, 4:4:end);
## Elements of d are now in the range 0 to 15
hstr = "0123456789ABCDEF"(d+1); # convert to char and return
endfunction
%!assert (dec2hex (2748), "ABC")
%!assert (dec2hex (2748, 5), "00ABC")
%!assert (dec2hex ([2748, 2746]), ["ABC"; "ABA"])
%!assert (dec2hex ({2748, 2746}), ["ABC"; "ABA"])
%!assert (dec2hex ({2748, 2746}, 4), ["0ABC"; "0ABA"])
## Test negative inputs
%!assert (dec2hex (-3), "FD")
%!assert (dec2hex (-3, 1), "FD")
%!assert (dec2hex (-3, 3), "0FD")
%!assert (dec2hex (-2^7 - 1), "FF7F")
%!assert (dec2hex (-2^15 - 1), "FFFF7FFF")
%!assert (dec2hex (-2^31 - 1), "FFFFFFFF7FFFFFFF")
%!assert (dec2hex (-2^52), "FFF0000000000000")
%!assert (dec2hex (-2^63), "8000000000000000")
%!assert (dec2hex (int64 (-2) ^ 63), "8000000000000000")
%!assert (dec2hex (int64 (-2) ^ 63 - 1), "8000000000000000")
%!assert (dec2hex (int64 (-2) ^ 63 + 1), "8000000000000001")
%!assert (dec2hex ([-1, -2; -3, -4]), ["FF"; "FD"; "FE"; "FC"])
%!assert (dec2hex ([1, 2; 3, -4]), ["01"; "03"; "02"; "FC"])
%!assert (dec2hex ({1, 2; 3, -4}), ["01"; "03"; "02"; "FC"])
## Test input validation
%!error <Invalid call> dec2hex ()
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