// Path: core/src/java/main/org/uncommons/maths/number/ConstantGenerator.java
// public class ConstantGenerator<T extends Number> implements NumberGenerator<T>
// {
//     private final T constant;
// 
//     /**
//      * Creates a number generator that always returns the same
//      * values.
//      * @param constant The value to be returned by all invocations
//      * of the {@link #nextValue()} method.
//      */
//     public ConstantGenerator(T constant)
//     {
//         this.constant = constant;
//     }
// 
//     /**
//      * @return The constant value specified when the generator was constructed.
//      */
//     public T nextValue()
//     {
//         return constant;
//     }
// }
// 
// Path: core/src/java/main/org/uncommons/maths/number/NumberGenerator.java
// public interface NumberGenerator<T extends Number>
// {
//     /**
//      * @return The next value from the generator.
//      */
//     T nextValue();
// }


import java.util.Random;
import org.uncommons.maths.number.ConstantGenerator;
import org.uncommons.maths.number.NumberGenerator;
// ============================================================================
//   Copyright 2006-2012 Daniel W. Dyer
//
//   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 org.uncommons.maths.random;


/**
 * Continuous random sequence that follows an
 * <a href="http://en.wikipedia.org/wiki/Exponential_distribution" target="_top">exponential
 * distribution</a>.
 * @author Daniel Dyer
 * @since 1.0.2
 */
public class ExponentialGenerator implements NumberGenerator<Double>
{
    private final NumberGenerator<Double> rate;
    private final Random rng;


    /**
     * Creates a generator of exponentially-distributed values from a distribution
     * with a rate controlled by the specified generator parameter.  The mean of
     * this distribution is {@literal 1 / rate}
     * and the variance is {@literal 1 / rate^2}.
     * @param rate A number generator that provides values to use as the rate for
     * the exponential distribution.  This generator must only return non-zero, positive
     * values.
     * @param rng The source of randomness used to generate the exponential values.
     */
    public ExponentialGenerator(NumberGenerator<Double> rate,
                                Random rng)
    {
        this.rate = rate;
        this.rng = rng;
    }


    /**
     * Creates a generator of exponentially-distributed values from a distribution
     * with the specified rate.  The mean of this distribution is {@literal 1 / rate}
     * and the variance is {@literal 1 / rate^2}.
     * @param rate The rate (lamda) of the exponential distribution.
     * @param rng The source of randomness used to generate the exponential values.
     */
    public ExponentialGenerator(double rate,
                                Random rng)
    {
// Path: core/src/java/main/org/uncommons/maths/number/ConstantGenerator.java
// public class ConstantGenerator<T extends Number> implements NumberGenerator<T>
// {
//     private final T constant;
// 
//     /**
//      * Creates a number generator that always returns the same
//      * values.
//      * @param constant The value to be returned by all invocations
//      * of the {@link #nextValue()} method.
//      */
//     public ConstantGenerator(T constant)
//     {
//         this.constant = constant;
//     }
// 
//     /**
//      * @return The constant value specified when the generator was constructed.
//      */
//     public T nextValue()
//     {
//         return constant;
//     }
// }
// 
// Path: core/src/java/main/org/uncommons/maths/number/NumberGenerator.java
// public interface NumberGenerator<T extends Number>
// {
//     /**
//      * @return The next value from the generator.
//      */
//     T nextValue();
// }


// Path: core/src/java/main/org/uncommons/maths/random/ExponentialGenerator.java
import java.util.Random;
import org.uncommons.maths.number.ConstantGenerator;
import org.uncommons.maths.number.NumberGenerator;

// ============================================================================
//   Copyright 2006-2012 Daniel W. Dyer
//
//   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 org.uncommons.maths.random;


/**
 * Continuous random sequence that follows an
 * <a href="http://en.wikipedia.org/wiki/Exponential_distribution" target="_top">exponential
 * distribution</a>.
 * @author Daniel Dyer
 * @since 1.0.2
 */
public class ExponentialGenerator implements NumberGenerator<Double>
{
    private final NumberGenerator<Double> rate;
    private final Random rng;


    /**
     * Creates a generator of exponentially-distributed values from a distribution
     * with a rate controlled by the specified generator parameter.  The mean of
     * this distribution is {@literal 1 / rate}
     * and the variance is {@literal 1 / rate^2}.
     * @param rate A number generator that provides values to use as the rate for
     * the exponential distribution.  This generator must only return non-zero, positive
     * values.
     * @param rng The source of randomness used to generate the exponential values.
     */
    public ExponentialGenerator(NumberGenerator<Double> rate,
                                Random rng)
    {
        this.rate = rate;
        this.rng = rng;
    }


    /**
     * Creates a generator of exponentially-distributed values from a distribution
     * with the specified rate.  The mean of this distribution is {@literal 1 / rate}
     * and the variance is {@literal 1 / rate^2}.
     * @param rate The rate (lamda) of the exponential distribution.
     * @param rng The source of randomness used to generate the exponential values.
     */
    public ExponentialGenerator(double rate,
                                Random rng)
    {
        this(new ConstantGenerator<Double>(rate), rng);