XSLT：我们可以使用abs值吗？

Question

I would like to know if in XLST can we use the math:abs(...) ? I saw this somewhere but it does not work . I have something like:

<tag>
  <xsl:value-of select="./product/blablaPath"/>
</tag>

I tried to do something like:

<tag>
  <xsl:value-of select="math:abs(./product/blablaPath)"/>
</tag>

but does not work. I'm using java 1.6 language.

Answer 1

Here is a single XPath expression implementing the abs() function:

($x >= 0)*$x - not($x >= 0)*$x

This evaluates to abs($x) .

Here is a brief demonstration of this in action :

<xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output omit-xml-declaration="yes" indent="yes"/>
  <xsl:strip-space elements="*"/>

 <xsl:template match="node()|@*">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*"/>
  </xsl:copy>
 </xsl:template>

 <xsl:template match="text()">
  <xsl:param name="x" select="."/>
  <xsl:value-of select=
  "($x >= 0)*$x - not($x >= 0)*$x"/>
 </xsl:template>
</xsl:stylesheet>

when this transformation is applied to the following XML document:

<t>
  <num>-3</num>
  <num>0</num>
  <num>5</num>
</t>

the wanted, correct result (abs() on every number) is produced :

<t>
  <num>3</num>
  <num>0</num>
  <num>5</num>
</t>

Answer 2

abs() is trivial enough. Implemented in pure XSLT it would look like this:

<xsl:template name="abs">
  <xsl:param name="number">

  <xsl:choose>
    <xsl:when test="$number &gt;= 0">
      <xsl:value-of select="$number" />
    <xsl:when>
    <xsl:otherwise>
      <xsl:value-of select="$number * -1" />
    </xsl:otherwise>
  </xsl:if>
</xsl:template>

in your context you would invoke it like this:

<tag>
  <xsl:call-template name="abs">
    <xsl:with-param name="number" select="number(product/blablaPath)" />
  </xsl:call-template>
</tag>

Answer 3

Anotherway:

(2*($x >= 0) - 1)*$x

When $x is positive, the test returns "true", so 2*true-1 returns 1, so final result is $x. When $x is negative, the test returns "false", so 2*false-1 returns -1, so final result is -$x.

Using

2*(any-test-here)-1

is a good way to have +1 when test is true , and -1 when false .

Answer 4

A very simple solution is to use the XSL 1.0 translate function. Ie

<xsl:value-of select="translate($x, '-', '')/>

Answer 5

math:abs is not built in to XSLT or XPATH. It is an XSLT extension, provided by the runtime you are transforming with.

Here is an article about .NET xslt extensions .

Here is one for Java (Xalan).