## Copyright (C) 1996-2020 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this distribution
## or <https://octave.org/COPYRIGHT.html/>.
##
##
## 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.
##
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
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## -*- texinfo -*-
## @deftypefn  {} {} is_leap_year ()
## @deftypefnx {} {} is_leap_year (@var{year})
## Return true if @var{year} is a leap year and false otherwise.
##
## If no year is specified, @code{is_leap_year} uses the current year.
##
## For example:
##
## @example
## @group
## is_leap_year (2000)
##    @result{} 1
## @end group
## @end example
## @seealso{weekday, eomday, calendar}
## @end deftypefn

function retval = is_leap_year (year)

  if (nargin > 1)
    print_usage ();
  endif

  if (nargin == 0)
    t = clock ();
    year = t(1);
  endif

  retval = (rem (year, 4) == 0 & rem (year, 100) != 0) | (rem (year, 400) == 0);

endfunction


%!assert (is_leap_year (2000), true)
%!assert (is_leap_year (1976), true)
%!assert (is_leap_year (1000), false)
%!assert (is_leap_year (1800), false)
%!assert (is_leap_year (1600), true)

%!error is_leap_year (1, 2)