1 files changed, 76 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/ode/sampling/FieldStepInterpolator.java b/src/main/java/org/apache/commons/math3/ode/sampling/FieldStepInterpolator.java
new file mode 100644
index 0000000..a005fb1
--- /dev/null
+++ b/src/main/java/org/apache/commons/math3/ode/sampling/FieldStepInterpolator.java
@@ -0,0 +1,76 @@
+/*
+ * 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();
+
+}