<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"

     version="1.0">

<xsl:output method="text"/>


<!-- Author: Bob DuCharme -->

<!-- Reference:  http://www.xml.com/pub/a/2001/05/07/xsltmath.html -->

<!-- Description: Compute pi. Based on Leibniz's algorithm that 

       pi/4 = 1 - 1/3 + 1/5 - 1/7 + 1/9 - 1/11... which I did as

       pi = 4 - 4/3 + 4/5 - 4/7 + 4/9 - 4/11...

-->


<xsl:variable name="iterations" select="4500"/>


<xsl:template name="pi">

  <!-- named template called by main template below -->

  <xsl:param name="i">1</xsl:param>

  <xsl:param name="piValue">0</xsl:param>


  <xsl:choose>

  <!-- If there are more iterations to do, add the passed

       value of pi to another round of calculations. -->

  <xsl:when test="$i &lt;= $iterations">

    <xsl:call-template name="pi">

      <xsl:with-param name="i" select="$i + 4"/>

      <xsl:with-param name="piValue" 

           select="$piValue + (4 div $i) - (4 div ($i + 2))"/>

    </xsl:call-template>

  </xsl:when>


  <!-- If no more iterations to do, add 

       computed value to result tree. -->

  <xsl:otherwise>

   <xsl:value-of select="$piValue"/>

  </xsl:otherwise>


  </xsl:choose>


</xsl:template>


<xsl:template match="/">

  <xsl:call-template name="pi"/>

</xsl:template>

  <!--
   * 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.
  -->

</xsl:stylesheet>