XSLT aggregating XML tag values and storing new ta

Question

I'm new to xslt and trying to process below XML using XSLT :

<xml>
<characters>
<char a="a1" b="b1" y="y1" z="z1"  weight="100">F</char>
<char a="a2" b="b2" y="y2" z="z2"  weight="80">r</char>
<char a="a3" b="b3" y="y3" z="z3"  weight="80">o</char>
<char a="a4" b="b4" y="y4" z="z4"  weight="100">m</char>
</characters>
</xml>

to produce output XML :

<word>
<value>From</value>
<coordinates>a1 b1 y4 z4</coordinates>
<avgWeight>90</avgWeight>
</word>

where coordinates form the first and last characters coordinates and avgWeight aggregate the values of weight tag.

Since XSLT variables are immutable, I'm unable perform below operation. Help me in finding solution.

Answer 1

Since XSLT variables are immutable, I'm unable perform below operation.

I don't see what variables, immutable or not, have to do with it. This is just straightforward XSLT:

XSLT 1.0

<xsl:stylesheet version="1.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="utf-8" indent="yes"/>

<xsl:template match="/xml">
    <xsl:for-each select="characters">
        <word>
            <value>
                <xsl:for-each select="char">
                    <xsl:value-of select="."/>
                </xsl:for-each>
            </value>
            <coordinates>
                <xsl:value-of select="char[1]/@a"/>
                <xsl:text> </xsl:text>
                <xsl:value-of select="char[1]/@b"/>
                <xsl:text> </xsl:text>
                <xsl:value-of select="char[last()]/@y"/>
                <xsl:text> </xsl:text>
                <xsl:value-of select="char[last()]/@z"/>
            </coordinates>
            <avgWeight>
                <xsl:value-of select="sum(characters/char/@weight) div count(characters/char) "/>
            </avgWeight>
        </word>
    </xsl:for-each>
</xsl:template>

</xsl:stylesheet>