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package org.apache.commons.math3.ode;

import org.apache.commons.math3.RealFieldElement;

This interface represents a first order differential equations set.
This interface should be implemented by all real first order differential equation problems before they can be handled by the integrators FirstOrderIntegrator.integrate method.
A first order differential equations problem, as seen by an
integrator is the time derivative dY/dt of a state
vector Y, both being one dimensional arrays. From the
integrator point of view, this derivative depends only on the
current time t and on the state vector
Y.
For real problems, the derivative depends also on parameters
that do not belong to the state vector (dynamical model constants
for example). These constants are completely outside of the scope
of this interface, the classes that implement it are allowed to
handle them as they want.
Type parameters:
<T> – the type of the field elements
See Also:
FirstOrderFieldIntegrator
Since:
3.6/** This interface represents a first order differential equations set.
 *
 * <p>This interface should be implemented by all real first order
 * differential equation problems before they can be handled by the
 * integrators {@link FirstOrderIntegrator#integrate} method.</p>
 *
 * <p>A first order differential equations problem, as seen by an
 * integrator is the time derivative <code>dY/dt</code> of a state
 * vector <code>Y</code>, both being one dimensional arrays. From the
 * integrator point of view, this derivative depends only on the
 * current time <code>t</code> and on the state vector
 * <code>Y</code>.</p>
 *
 * <p>For real problems, the derivative depends also on parameters
 * that do not belong to the state vector (dynamical model constants
 * for example). These constants are completely outside of the scope
 * of this interface, the classes that implement it are allowed to
 * handle them as they want.</p>
 *
 * @see FirstOrderFieldIntegrator
 *
 * @param <T> the type of the field elements
 * @since 3.6
 */

public interface FirstOrderFieldDifferentialEquations<T extends RealFieldElement<T>> {

    
Get the dimension of the problem.
Returns:
dimension of the problem/** Get the dimension of the problem.
     * @return dimension of the problem
     */
    int getDimension();

    
Initialize equations at the start of an ODE integration.

This method is called once at the start of the integration. It
may be used by the equations to initialize some internal data
if needed.

Params:
t0 – value of the independent time variable at integration start
y0 – array containing the value of the state vector at integration start
finalTime – target time for the integration/** Initialize equations at the start of an ODE integration.
     * <p>
     * This method is called once at the start of the integration. It
     * may be used by the equations to initialize some internal data
     * if needed.
     * </p>
     * @param t0 value of the independent <I>time</I> variable at integration start
     * @param y0 array containing the value of the state vector at integration start
     * @param finalTime target time for the integration
     */
    void init(T t0, T[] y0, T finalTime);

    
Get the current time derivative of the state vector.
Params:
t – current value of the independent time variable
y – array containing the current value of the state vector
Returns:
time derivative of the state vector/** Get the current time derivative of the state vector.
     * @param t current value of the independent <I>time</I> variable
     * @param y array containing the current value of the state vector
     * @return time derivative of the state vector
     */
    T[] computeDerivatives(T t, T[] y);

}