function dydt = shm_deriv ( t, y )

%*****************************************************************************80
%
%% shm_deriv() evaluates the right hand side of the SHM system.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    30 April 2021
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real T, the current time.
%
%    real Y[2], the current solution variables, rabbits and foxes.
%
%  Output:
%
%    real DYDT[2], the right hand side of the ODE.
%
  dydt = zeros ( 2 );

  dydt(1) =   y(2);
  dydt(2) = - y(1);

  return
end


