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## -*- texinfo -*-
## @deftypefn {} {} dec2bin (@var{d}, @var{len})
## Return a binary number corresponding to the integer @var{d} as a string of
## ones and zeros.  If @var{d} is negative, return the two's complement binary
## value of @var{d}.
##
## For example:
##
## @example
## @group
## dec2bin (14)
##      @result{} "1110"
##
## dec2bin (-14)
##      @result{} "11110010"
## @end group
## @end example
##
## If @var{d} is a matrix or cell array, return a string matrix with one row
## per 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.
##
## @seealso{bin2dec, dec2base, dec2hex}
## @end deftypefn

function b = dec2bin (d, len)

## dec2base does cell->mat conversion, this allows easier content comparison
if (iscell (d))
  d = cell2mat (d);
endif

d = d(:);  ## output is always a column vector, (:) simplifies value checks

if (any (d < intmin ("int64")))
    error ("dec2bin: negative inputs cannot be less than intmin('int64')");
endif

if (any (d < 0))
  if (any (d < intmin ("int64")))
    error ("out of range");
  elseif (any (d < intmin ("int32")))
    d(d < 0) += double (intmax ("uint64")) + 1 ;
  elseif (any (d < intmin ("int16")))
    d(d < 0) += double (intmax ("uint32")) + 1;
  elseif (any (d < intmin ("int8")))
    d(d < 0) += double (intmax ("uint16"))+ 1;
  else
    d(d < 0) += double (intmax ("uint8")) +1;
  endif
endif

  if (nargin == 1)
    b = dec2base (d, 2);
  elseif (nargin == 2)
    b = dec2base (d, 2, len);
  else
    print_usage ();
  endif

endfunction


%!assert (dec2bin (3), "11")
%!assert (dec2bin (14), "1110")
%!assert (dec2bin (14, 6), "001110")
%!assert (dec2bin ([1, 2; 3, 4]), ["001"; "011"; "010"; "100"])
%!assert (dec2bin ({1, 2; 3, 4}), ["001"; "011"; "010"; "100"])
%!assert (dec2bin ({1, 2; 3, 4}, 4), ["0001"; "0011"; "0010"; "0100"])

## Test negative inputs
%!assert (dec2bin (-3), "11111101")
%!assert (dec2bin (-3, 3), "11111101")
%!assert (dec2bin (-3, 9), "011111101")
%!assert (dec2bin (-129), "1111111101111111")
%!assert (dec2bin (-2^15 -1), "11111111111111110111111111111111")
%!assert (dec2bin (-2^31 -1), "1111111111111111111111111111111101111111111111111111111111111111")
%!assert (dec2bin (-2^63), "1000000000000000000000000000000000000000000000000000000000000000")
%!assert (dec2bin (-2^63-1), "1000000000000000000000000000000000000000000000000000000000000000")
%!assert (dec2bin ([-1, -2; -3, -4]), ["11111111"; "11111101"; "11111110"; "11111100"])
%!assert (dec2bin ([1, 2; 3, -4]), ["00000001"; "00000011"; "00000010"; "11111100"])
%!assert (dec2bin ({1, 2; 3, -4}), ["00000001"; "00000011"; "00000010"; "11111100"])

## Test input validation
%!error dec2bin ()
%!error dec2bin (1, 2, 3)
%!error dec2bin (2 * double (intmin ("int64")))