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Number 'normalisation' in XSL

Posted on 2001-08-09
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Last Modified: 2008-03-10
Hello!
I have to normalise the number that i have in XML, i.e. i have to calculate its mantissa and exponent.
So if i have 123456 it should be normalised as 1,23456e+5.
Unfortunatelly, i have to use only pure xsl, no extension functions or scripts are allowed.
Please give me working example asap.
Thanks.
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Question by:pavlin
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5 Comments
 
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Expert Comment

by:BigRat
Comment Utility
You should look at the xsl:decimal-format element and the associated function format-number. I have studied both of these and I can't see anyway of doing it :(
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by:sdussinger
Comment Utility
I've looked at the number formatting stuff as well, and it doesn't appear to work the way we'd like. However, in an extreme masochistic XSL session, I've managed to build a transform that will normalize a number.

Here it is in all its grotesque glory:

-----------------------------------------------------------

<!--
   Generic template to normalize a number

   Pass a param called "num" containing the number you wish
   to normalize
-->
<xsl:template name="normalize-number">
  <xsl:param name="num" select="0"/>

  <xsl:call-template name="do-normalize">
    <xsl:with-param name="mantissa" select="$num"/>
    <xsl:with-param name="exp" select="0"/>
  </xsl:call-template>

</xsl:template>

<!--
   Simple template for formatting the exponent. This
   is needed to ensure that the '+' sign shows up for
   positive exponents.
-->
<xsl:template name="format-exp">
  <xsl:param name="exp" select="0"/>

  <xsl:if test="$exp &gt;= 0">
    <xsl:text>+</xsl:text>
  </xsl:if>
  <xsl:value-of select="$exp"/>

</xsl:template>

<!--

   This is the body of the normalizer. It recursively
   processes the number until its in the correct form
-->
<xsl:template name="do-normalize">

  <xsl:param name="mantissa" select="0"/>
  <xsl:param name="exp" select="0"/>

  <xsl:choose>

    <!-- If the mantissa is 0, we're done. Just print it out -->
    <xsl:when test="$mantissa = 0.0 or $mantissa = -0.0">
      <xsl:value-of select="format-number(0.0, '#,##0.00000')"/>
      <xsl:text>e</xsl:text>
      <xsl:call-template name="format-exp">
        <xsl:with-param name="exp" select="$exp"/>
      </xsl:call-template>
    </xsl:when>

    <!-- If we've gotten the number normalized, then print it out.
         This is for a positive number -->
    <xsl:when test="$mantissa &gt;= 1.0 and $mantissa &lt; 10.0">
      <xsl:value-of select="format-number (number($mantissa), '#,##0.00000')"/>
      <xsl:text>e</xsl:text>
      <xsl:call-template name="format-exp">
        <xsl:with-param name="exp" select="$exp"/>
      </xsl:call-template>
    </xsl:when>

    <!-- We've gotten a negative number normalized, print it -->
    <xsl:when test="$mantissa &gt; -10.0 and $mantissa &lt;= -1.0">
      <xsl:value-of select="format-number (number($mantissa), '#,##0.00000')"/>
      <xsl:text>e</xsl:text>
      <xsl:call-template name="format-exp">
        <xsl:with-param name="exp" select="$exp"/>
      </xsl:call-template>
    </xsl:when>

    <!-- In this case we've got a number greater than abs(10.0). We
         add one to the exponent, divide the mantissa by 10, and recurse -->
    <xsl:when test="$mantissa &gt;= 10.0 or $mantissa &lt;= -10.0">
      <xsl:call-template name="do-normalize">
        <xsl:with-param name="mantissa" select="$mantissa div 10"/>
        <xsl:with-param name="exp" select="$exp + 1"/>
      </xsl:call-template>
    </xsl:when>

    <!-- In this case we have a number whose abs() < 1.0. We subtract 1
         from the exponent, multiply the mantissa by 10 and recurse. -->
    <xsl:when test="$mantissa &gt; -1.0 and $mantissa &lt; 1.0">
      <xsl:call-template name="do-normalize">
        <xsl:with-param name="mantissa" select="$mantissa * 10"/>
        <xsl:with-param name="exp" select="$exp - 1"/>
      </xsl:call-template>
    </xsl:when>
  </xsl:choose>

</xsl:template>


-----------------------------------------------------------

It's probably one of the most wretched things one would ever want to do with XSL, but it works. I've tested it using Stylus and it handled every test case I threw at it.

--Steve
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Accepted Solution

by:
djokov earned 200 total points
Comment Utility
Hi!
I think you want to calculate mantissa and exponent, not just to "print" the normalized value. In such case you will need to return two values from your "Normalization" template. So, my suggestion is:

Call template in this way:
<xsl:variable name="nn">
   <xsl:call-template name="Normalize">
       <xsl:with-param name="man" select="$NumberToBeNormalized"/>
   </xsl:call-template>
</xsl:variable>
<xsl:variable name="Normalized" select="$nn"/>
...
Then you could get Mantissa and Exponnet in this way:
<xsl:variable name="Mantissa" select="$Normalized/Mantissa"/>
<xsl:variable name="Exponent" select="$Normalized/Exponent"/>
... and then you could do what you want with $Mantissa and $Exponent.

Finally, the "Normalize" template:
<xsl:template name="Normalize">
   <xsl:with-param name="man"/>
   <xsl:with-param name="exp" select="0"/>

   <xsl:choose>
       <xsl:when test="($man > 10) or ($man &lt; -10)">
           <xsl:call-template name="Normalize">
               <xsl:with-param name="man" select="$man div 10"/>
               <xsl:with-param name="exp" select="$exp + 1"/>
           </xsl:call-template>
       </xsl:when>
       <xsl:when test="(($man &lt; 1) and ($man > 0)) or (($man &lt; 0) and ($man > -1))">
           <xsl:call-template name="Normalize">
               <xsl:with-param name="man" select="$man * 10"/>
               <xsl:with-param name="exp" select="$exp - 1"/>
           </xsl:call-template>
       </xsl:when>
       <xsl:otherwise>
           <Mantissa><xsl:value-of select="$man"/></Mantissa>
           <Exponent><xsl:value-of select="$exp"/></Exponent>
       </xsl:otherwise>
   </xsl:choose>
</xsl:template>

Cheers.
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Expert Comment

by:djokov
Comment Utility
<xsl:when test="($man > 10) or ($man &lt; -10)">
should be:
<xsl:when test="($man >= 10) or ($man &lt;= -10)">

sorry.
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LVL 4

Expert Comment

by:sdussinger
Comment Utility
It seems  as if my choice of the comments was misleading. When I said "print" in the comments I was really referring to formatting the normalized number.  One could easily use the code to assign a value to a variable as in the following:

<xsl:variable name="normalized">
  <xsl:call-template name="normalize-number">
    <xsl:with-param name="num" value="$value-to-normalize"/>
  </xsl:call-template>
</xsl:variable>

Sorry for the confusion...

--Steve
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