OperatorToken.java

/*
   Copyright 2011 frank asseg

   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 de.congrace.exp4j;

import java.util.Map;
import java.util.Stack;

/**
 * {@link Token} for Operations like +,-,*,/,% and ^
 * 
 * @author fas@congrace.de
 */
class OperatorToken extends CalculationToken {

	CustomOperator operation;

	/**
	 * construct a new {@link OperatorToken}
	 * 
	 * @param value
	 *            the symbol (e.g.: '+')
	 * @param operation
	 *            the {@link CustomOperator} of this {@link Token}
	 */
	OperatorToken(String value, CustomOperator operation) {
		super(value);
		this.operation = operation;
	}

	/**
	 * apply the {@link CustomOperator}
	 * 
	 * @param values
	 *            the doubles to operate on
	 * @return the result of the {@link CustomOperator}
	 */
	double applyOperation(double... values) {
		return operation.applyOperation(values);
	}

	@Override
	public boolean equals(Object obj) {
		if (obj instanceof OperatorToken) {
			final OperatorToken t = (OperatorToken) obj;
			return t.getValue().equals(this.getValue());
		}
		return false;
	}

	@Override
	public int hashCode() {
		return getValue().hashCode();
	}

	@Override
	void mutateStackForCalculation(Stack<Double> stack, Map<String, Double> variableValues) {
		final double[] operands = new double[operation.operandCount];
		for (int i = 0; i < operation.operandCount; i++) {
			operands[operation.operandCount - i - 1] = stack.pop();
		}
		stack.push(operation.applyOperation(operands));
	}

	@Override
	void mutateStackForInfixTranslation(Stack<Token> operatorStack, StringBuilder output) {
		Token before;
		while (!operatorStack.isEmpty() && (before = operatorStack.peek()) != null
				&& (before instanceof OperatorToken || before instanceof FunctionToken)) {
			if (before instanceof FunctionToken) {
				operatorStack.pop();
				output.append(before.getValue()).append(" ");
			} else {
				final OperatorToken stackOperator = (OperatorToken) before;
				if (this.isLeftAssociative() && this.getPrecedence() <= stackOperator.getPrecedence()) {
					output.append(operatorStack.pop().getValue()).append(" ");
				} else if (!this.isLeftAssociative() && this.getPrecedence() < stackOperator.getPrecedence()) {
					output.append(operatorStack.pop().getValue()).append(" ");
				} else {
					break;
				}
			}
		}
		operatorStack.push(this);
	}

	private boolean isLeftAssociative() {
		return operation.leftAssociative;
	}

	private int getPrecedence() {
		return operation.precedence;
	}
}