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 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
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 *      http://www.apache.org/licenses/LICENSE-2.0
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 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.commons.math3.ode.sampling;

import org.apache.commons.math3.RealFieldElement;
import org.apache.commons.math3.ode.FieldODEStateAndDerivative;

This interface represents an interpolator over the last step
during an ODE integration.
The various ODE integrators provide objects implementing this
interface to the step handlers. These objects are often custom
objects tightly bound to the integrator internal algorithms. The
handlers can use these objects to retrieve the state vector at
intermediate times between the previous and the current grid points
(this feature is often called dense output).
Type parameters:
<T> – the type of the field elements
See Also:
FirstOrderFieldIntegrator
FieldStepHandler
Since:
3.6/** This interface represents an interpolator over the last step
 * during an ODE integration.
 *
 * <p>The various ODE integrators provide objects implementing this
 * interface to the step handlers. These objects are often custom
 * objects tightly bound to the integrator internal algorithms. The
 * handlers can use these objects to retrieve the state vector at
 * intermediate times between the previous and the current grid points
 * (this feature is often called dense output).</p>
 *
 * @param <T> the type of the field elements
 * @see org.apache.commons.math3.ode.FirstOrderFieldIntegrator
 * @see FieldStepHandler
 * @since 3.6
 */

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

  
Get the state at previous grid point time.
Returns:
state at previous grid point time/**
   * Get the state at previous grid point time.
   * @return state at previous grid point time
   */
  FieldODEStateAndDerivative<T> getPreviousState();

  
Get the state at current grid point time.
Returns:
state at current grid point time/**
   * Get the state at current grid point time.
   * @return state at current grid point time
   */
  FieldODEStateAndDerivative<T> getCurrentState();

  
Get the state at interpolated time.
Setting the time outside of the current step is allowed, but
should be used with care since the accuracy of the interpolator will
probably be very poor far from this step. This allowance has been
added to simplify implementation of search algorithms near the
step endpoints.
Params:
time – time of the interpolated point
Returns:
state at interpolated time/**
   * Get the state at interpolated time.
   * <p>Setting the time outside of the current step is allowed, but
   * should be used with care since the accuracy of the interpolator will
   * probably be very poor far from this step. This allowance has been
   * added to simplify implementation of search algorithms near the
   * step endpoints.</p>
   * @param time time of the interpolated point
   * @return state at interpolated time
   */
  FieldODEStateAndDerivative<T> getInterpolatedState(T time);

  
Check if the natural integration direction is forward.
This method provides the integration direction as specified by
the integrator itself, it avoid some nasty problems in
degenerated cases like null steps due to cancellation at step
initialization, step control or discrete events
triggering.
Returns:
true if the integration variable (time) increases during
integration/** Check if the natural integration direction is forward.
   * <p>This method provides the integration direction as specified by
   * the integrator itself, it avoid some nasty problems in
   * degenerated cases like null steps due to cancellation at step
   * initialization, step control or discrete events
   * triggering.</p>
   * @return true if the integration variable (time) increases during
   * integration
   */
  boolean isForward();

}