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/*
* 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.events;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.Precision;
/** Transformer for {@link EventHandler#g(double, double[]) g functions}.
* @see EventFilter
* @see FilterType
* @since 3.2
*/
enum Transformer {
/** Transformer computing transformed = 0.
* <p>
* This transformer is used when we initialize the filter, until we get at
* least one non-zero value to select the proper transformer.
* </p>
*/
UNINITIALIZED {
/** {@inheritDoc} */
@Override
protected double transformed(final double g) {
return 0;
}
},
/** Transformer computing transformed = g.
* <p>
* When this transformer is applied, the roots of the original function
* are preserved, with the same {@code increasing/decreasing} status.
* </p>
*/
PLUS {
/** {@inheritDoc} */
@Override
protected double transformed(final double g) {
return g;
}
},
/** Transformer computing transformed = -g.
* <p>
* When this transformer is applied, the roots of the original function
* are preserved, with reversed {@code increasing/decreasing} status.
* </p>
*/
MINUS {
/** {@inheritDoc} */
@Override
protected double transformed(final double g) {
return -g;
}
},
/** Transformer computing transformed = min(-{@link Precision#SAFE_MIN}, -g, +g).
* <p>
* When this transformer is applied, the transformed function is
* guaranteed to be always strictly negative (i.e. there are no roots).
* </p>
*/
MIN {
/** {@inheritDoc} */
@Override
protected double transformed(final double g) {
return FastMath.min(-Precision.SAFE_MIN, FastMath.min(-g, +g));
}
},
/** Transformer computing transformed = max(+{@link Precision#SAFE_MIN}, -g, +g).
* <p>
* When this transformer is applied, the transformed function is
* guaranteed to be always strictly positive (i.e. there are no roots).
* </p>
*/
MAX {
/** {@inheritDoc} */
@Override
protected double transformed(final double g) {
return FastMath.max(+Precision.SAFE_MIN, FastMath.max(-g, +g));
}
};
/** Transform value of function g.
* @param g raw value of function g
* @return transformed value of function g
*/
protected abstract double transformed(double g);
}
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