Implementation of Excel Days360 and Npv functions

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@811996 13f79535-47bb-0310-9956-ffa450edef68

src/documentation/content/xdocs/status.xml

@@ -33,6 +33,8 @@
 
     <changes>
         <release version="3.5-beta7" date="2009-??-??">
+           <action dev="POI-DEVELOPERS" type="add">47768 - Implementation of Excel "Days360" and "Npv" functions</action>
+           <action dev="POI-DEVELOPERS" type="fix">47751 - Do not allow HSSF's cell text longer than 32,767 characters</action>
            <action dev="POI-DEVELOPERS" type="add">47757 - Added an example demonstrating how to convert an XLSX workbook to CSV</action>
            <action dev="POI-DEVELOPERS" type="fix">44770 - Fixed PPT parser to tolerate Comment2000 containers with missing comment text</action>
            <action dev="POI-DEVELOPERS" type="fix">47773 - Fix for extraction paragraphs and sections from headers/footers with XWPFWordExtractor</action>

src/java/org/apache/poi/hssf/record/formula/functions/Days360.java

@@ -0,0 +1,74 @@
+package org.apache.poi.hssf.record.formula.functions;
+
+import java.util.Calendar;
+import java.util.GregorianCalendar;
+
+import org.apache.poi.hssf.record.formula.eval.EvaluationException;
+import org.apache.poi.ss.usermodel.DateUtil;
+
+/**
+ * Calculates the number of days between two dates based on a 360-day year
+ * (twelve 30-day months), which is used in some accounting calculations. Use
+ * this function to help compute payments if your accounting system is based on
+ * twelve 30-day months.
+ * 
+ * 
+ * @author PUdalau
+ */
+public class Days360 extends NumericFunction.TwoArg {
+
+    @Override
+    protected double evaluate(double d0, double d1) throws EvaluationException {
+        Calendar startingDate = getStartingDate(d0);
+        Calendar endingDate = getEndingDateAccordingToStartingDate(d1, startingDate);
+        long startingDay = startingDate.get(Calendar.MONTH) * 30 + startingDate.get(Calendar.DAY_OF_MONTH);
+        long endingDay = (endingDate.get(Calendar.YEAR) - startingDate.get(Calendar.YEAR)) * 360
+                + endingDate.get(Calendar.MONTH) * 30 + endingDate.get(Calendar.DAY_OF_MONTH);
+        return endingDay - startingDay;
+    }
+
+    private Calendar getDate(double date) {
+        Calendar processedDate = new GregorianCalendar();
+        processedDate.setTime(DateUtil.getJavaDate(date, false));
+        return processedDate;
+    }
+
+    private Calendar getStartingDate(double date) {
+        Calendar startingDate = getDate(date);
+        if (isLastDayOfMonth(startingDate)) {
+            startingDate.set(Calendar.DAY_OF_MONTH, 30);
+        }
+        return startingDate;
+    }
+
+    private Calendar getEndingDateAccordingToStartingDate(double date, Calendar startingDate) {
+        Calendar endingDate = getDate(date);
+        endingDate.setTime(DateUtil.getJavaDate(date, false));
+        if (isLastDayOfMonth(endingDate)) {
+            if (startingDate.get(Calendar.DATE) < 30) {
+                endingDate = getFirstDayOfNextMonth(endingDate);
+            }
+        }
+        return endingDate;
+    }
+
+    private boolean isLastDayOfMonth(Calendar date) {
+        Calendar clone = (Calendar) date.clone();
+        clone.add(java.util.Calendar.MONTH, 1);
+        clone.add(java.util.Calendar.DAY_OF_MONTH, -1);
+        int lastDayOfMonth = clone.get(Calendar.DAY_OF_MONTH);
+        return date.get(Calendar.DAY_OF_MONTH) == lastDayOfMonth;
+    }
+
+    private Calendar getFirstDayOfNextMonth(Calendar date) {
+        Calendar newDate = (Calendar) date.clone();
+        if (date.get(Calendar.MONTH) < Calendar.DECEMBER) {
+            newDate.set(Calendar.MONTH, date.get(Calendar.MONTH) + 1);
+        } else {
+            newDate.set(Calendar.MONTH, 1);
+            newDate.set(Calendar.YEAR, date.get(Calendar.YEAR) + 1);
+        }
+        newDate.set(Calendar.DATE, 1);
+        return newDate;
+    }
+}

src/java/org/apache/poi/hssf/record/formula/functions/Npv.java

@@ -0,0 +1,47 @@
+/* ====================================================================
+   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.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.EvaluationException;
+
+/**
+ * Calculates the net present value of an investment by using a discount rate
+ * and a series of future payments (negative values) and income (positive
+ * values). Minimum 2 arguments, first arg is the rate of discount over the
+ * length of one period others up to 254 arguments representing the payments and
+ * income.
+ * 
+ * @author SPetrakovsky
+ */
+public class Npv extends NumericFunction.MultiArg {
+
+	public Npv() {
+		super(2, 255);
+	}
+
+	@Override
+	protected double evaluate(double[] ds) throws EvaluationException {
+		double rate = ds[0];
+		double sum = 0;
+		for (int i = 1; i < ds.length; i++) {
+			sum += ds[i] / Math.pow(rate + 1, i);
+		}
+		return sum;
+	}
+
+}