/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
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.
*
* <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.
* @return state at previous grid point time
*/
FieldODEStateAndDerivative<T> getPreviousState();
/**
* Get the state at current grid point time.
* @return state at current grid point time
*/
FieldODEStateAndDerivative<T> getCurrentState();
/**
* 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.
* <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();
}