| /* ==================================================================== |
| Licensed to the Apache Software Foundation (ASF) under one or more |
| contributor license agreements. See the NOTICE file distributed with |
| this work for additional information regarding copyright ownership. |
| The ASF licenses this file to You 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.apache.poi.ss.formula.functions; |
| |
| import org.apache.poi.ss.formula.OperationEvaluationContext; |
| import org.apache.poi.ss.formula.eval.*; |
| |
| import java.math.BigInteger; |
| import java.util.HashMap; |
| |
| /** |
| * Implementation for Excel FACTDOUBLE() function.<p> |
| * <p> |
| * <b>Syntax</b>:<br> <b>FACTDOUBLE </b>(<b>number</b>)<br> |
| * <p> |
| * Returns the double factorial of a number. |
| * <p> |
| * Number is the value for which to return the double factorial. If number is not an integer, it is truncated. |
| * <p> |
| * Remarks |
| * <ul> |
| * <li>If number is nonnumeric, FACTDOUBLE returns the #VALUE! error value.</li> |
| * <li>If number is negative, FACTDOUBLE returns the #NUM! error value.</li> |
| * </ul> |
| * Use a cache for more speed of previously calculated factorial |
| * |
| * @author cedric dot walter @ gmail dot com |
| */ |
| public class FactDouble extends Fixed1ArgFunction implements FreeRefFunction { |
| |
| public static final FreeRefFunction instance = new FactDouble(); |
| |
| //Caching of previously calculated factorial for speed |
| static HashMap<Integer, BigInteger> cache = new HashMap<>(); |
| |
| public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval numberVE) { |
| int number; |
| try { |
| number = OperandResolver.coerceValueToInt(numberVE); |
| } catch (EvaluationException e) { |
| return ErrorEval.VALUE_INVALID; |
| } |
| |
| if (number < 0) { |
| return ErrorEval.NUM_ERROR; |
| } |
| |
| return new NumberEval(factorial(number).longValue()); |
| } |
| |
| public static BigInteger factorial(int n) { |
| if (n == 0 || n < 0) { |
| return BigInteger.ONE; |
| } |
| |
| if (cache.containsKey(n)) { |
| return cache.get(n); |
| } |
| |
| BigInteger result = BigInteger.valueOf(n).multiply(factorial(n - 2)); |
| cache.put(n, result); |
| return result; |
| } |
| |
| public ValueEval evaluate(ValueEval[] args, OperationEvaluationContext ec) { |
| if (args.length != 1) { |
| return ErrorEval.VALUE_INVALID; |
| } |
| return evaluate(ec.getRowIndex(), ec.getColumnIndex(), args[0]); |
| } |
| } |