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Stochastice Performance Logic is a formalism for capturing performance assumptions. It is, for example, possible to capture assumption that newer version of a function bar is faster than the previous version or that library foobar is faster than library barfoo when rendering antialiased text. The purpose of this framework is to allow evaluation of SPL formulas inside Java applications.

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/*
 * Copyright 2015 Charles University in Prague
 * Copyright 2015 Vojtech Horky
 * 
 * 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 cz.cuni.mff.d3s.spl.formula;

import cz.cuni.mff.d3s.spl.Result;

/** Formula node: conjunction of two subformulas.
 *
 */
public class LogicAnd extends LogicOp {

	public LogicAnd(Formula left, Formula right) {
		super(left, right);
	}

	/*
	 * We are using Kleene three-value logic.
	 */
	@Override
	public Result evaluate(double significanceLevel) {
		Result leftResult = left.evaluate(significanceLevel);
		
		/*
		 * If the left one is FALSE, we do not need
		 * to evaluate the right one.
		 */
		if (leftResult == Result.FALSE) {
			return Result.FALSE;
		}
		
		Result rightResult = right.evaluate(significanceLevel);
		
		/*
		 * If left is TRUE, the result solely depends on
		 * the evaluation of the right one.
		 * For CANNOT_COMPUTE, it is a bit more complicated.
		 */
		if (leftResult == Result.TRUE) {
			return rightResult;
		} else {
			assert leftResult == Result.CANNOT_COMPUTE;
			if (rightResult == Result.FALSE) {
				return Result.FALSE;
			} else {
				return Result.CANNOT_COMPUTE;
			}
		}
	}
}