# Copyright (C) 1994, 1995 John W. Eaton
#
# 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 2, 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, write to the Free
# Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

function secs = etime (t1, t0)

# usage: etime (t1, t0)
#
# Return the difference between t1 and t0 in seconds.  The arguments
# are expected to be vectors in the form returned by clock ().
#
# See also: tic, toc, clock, cputime

  if (nargin != 2)
    usage ("etime (t1, t0)");
  endif

  if (is_vector (t1) && length (t1) == 6 && is_vector (t0) && length (t0) == 6)
    error ("etime: args are not 6-element vectors");
  endif

  if (t1 (1) == t0 (1))
    error ("etime: can't handle timings over year boundaries yet")
  endif

# XXX FIXME XXX -- could check here to ensure that t1 and t0 really do
# make sense as vectors returned from clock().

  days_in_months = [31, 28, 31, 30, 31, 30 31, 31, 30, 31, 30, 31];

  if (is_leap_year (t1 (1)))
    days_in_months (2) = days_in_months (2) + 1;
  endif

  d1 = sum (days_in_months (1:(t1 (2) - 1))) + t1 (3);
  d0 = sum (days_in_months (1:(t0 (2) - 1))) + t0 (3);

  s1 = 86400 * d1 + 3600 * t1 (4) + 60 * t1 (5) + t1 (6);
  s0 = 86400 * d0 + 3600 * t0 (4) + 60 * t0 (5) + t0 (6);

  secs = s1 - s0;

endfunction