//=============================================================================
// Copyright 2006-2010 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.watchmaker.examples.geneticprogramming;
/**
* A program {@link Node} that simply returns the value of one of the
* program's parameters.
* @author Daniel Dyer
*/
public class Parameter extends LeafNode
{
private final int parameterIndex;
/**
* @param parameterIndex Which of the program's (zero-indexed) parameter
* values should be returned upon evaluation of this node.
*/
public Parameter(int parameterIndex)
{
this.parameterIndex = parameterIndex;
}
/**
* Returns the value of one of the program parameters.
* @param programParameters The parameters to this program.
* @return The program parameter at the index condigured for this node.
*/
public double evaluate(double[] programParameters)
{
if (parameterIndex >= programParameters.length)
{
throw new IllegalArgumentException("Invalid parameter index: " + parameterIndex);
}
return programParameters[parameterIndex];
}
/**
* {@inheritDoc}
*/
public String getLabel()
{
return "P" + parameterIndex;
}
/**
* {@inheritDoc}
* For a parameter node the String representation is simply "arg0", "arg1", etc.
* depending on which program parameter it refers to.
*/
public String print()
{
return "arg" + parameterIndex;
}
/**
* Two parameters are equal if they evaluate to the same program argument
* (i.e. they have the same parameter index).
* @param other The object that this object is compared to.
* @return True if the parameters are equivalent, false otherwise.
*/
@Override
public boolean equals(Object other)
{
if (this == other)
{
return true;
}
if (other == null || getClass() != other.getClass())
{
return false;
}
return parameterIndex == ((Parameter) other).parameterIndex;
}
/**
* Over-ridden to be consistent with {@link #equals(Object)}.
* @return This object's hash code.
*/
@Override
public int hashCode()
{
return parameterIndex;
}
}