io.yields.math.concepts.operator.CurveLengthTest.java Source code

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Here is the source code for io.yields.math.concepts.operator.CurveLengthTest.java

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/*
 * Copyright 2015 by Yields.
 *
 * Licensed 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 io.yields.math.concepts.operator;

import org.apache.commons.math3.analysis.function.Asinh;
import org.fest.assertions.Assertions;
import org.fest.assertions.Delta;
import org.junit.Test;
import org.junit.runner.RunWith;

import java.util.function.Function;

import io.yields.math.framework.FunctionalContext;
import io.yields.math.framework.Variable;
import io.yields.math.framework.functional.DoubleIdentity;
import io.yields.math.framework.junit.Spec;
import io.yields.math.framework.junit.SpecRunner;

import static io.yields.math.concepts.operator.Operators.length;
import static io.yields.math.framework.assertions.Assertions.assertThat;
import static io.yields.math.framework.property.Properties.identity;

@RunWith(SpecRunner.class)
public class CurveLengthTest {

    public static class LengthOfParabola extends DoubleIdentity {

        @Variable("]0,100[")
        public double endOfIntegration;

        private Function<Double, Double> function = x -> .5 * x * x;

        @Override
        protected Double originalComputation() {
            return length().between(0, endOfIntegration).apply(function);
        }

        @Override
        protected Double alternativeComputation() {
            return .5 * (Math.sqrt(1 + Math.pow(endOfIntegration, 2)) * endOfIntegration
                    + new Asinh().value(endOfIntegration));
        }
    }

    @Spec(name = "Check curve length along parabola", functional = LengthOfParabola.class)
    public void lengthOfParabola(FunctionalContext<Double> function) {
        assertThat(function).is(identity(.001));
    }

    @Test
    public void testFailoverCalculation() {
        Function<Double, Double> curve = x -> Math.sin(x);
        Assertions.assertThat(length().between(0, 2 * Math.PI).apply(curve))
                .isEqualTo(length().between(0, 2 * Math.PI).simpsonIntegration(curve), Delta.delta(1.e-8));
    }

}