smarty/docs/en/designers/language-custom-functions/language-function-math.xml

<?xml version="1.0" encoding="iso-8859-1"?>
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<sect1 id="language.function.math">
 <title>{math}</title>
  <para>
   {math} allows the template designer to do math equations in the
   template. Any numeric template variables may be used in the
   equations, and the result is printed in place of the tag. The
   variables used in the equation are passed as parameters, which can
   be template variables or static values. +, -, /, *, abs, ceil, cos,
   exp, floor, log, log10, max, min, pi, pow, rand, round, sin, sqrt,
   srans and tan are all valid operators. Check the PHP documentation
   for further information on these math functions.
  </para>
  <para>
   If you supply the special "assign" attribute, the output of the
   math function will be assigned to this template variable instead of
   being output to the template.
 </para>
 
 <informaltable frame="all">
  <tgroup cols="5">
   <colspec colname="param" align="center" />
   <colspec colname="type" align="center" />
   <colspec colname="required" align="center" />
   <colspec colname="default" align="center" />
   <colspec colname="desc" />
   <thead>
    <row>
     <entry>Attribute Name</entry>
     <entry>Type</entry>
     <entry>Required</entry>
     <entry>Default</entry>
     <entry>Description</entry>
    </row>
   </thead>
   <tbody>
    <row>
     <entry>equation</entry>
     <entry>string</entry>
     <entry>Yes</entry>
     <entry><emphasis>n/a</emphasis></entry>
     <entry>the equation to execute</entry>
    </row>
    <row>
     <entry>format</entry>
     <entry>string</entry>
     <entry>No</entry>
     <entry><emphasis>n/a</emphasis></entry>
     <entry>the format of the result (sprintf)</entry>
    </row>
    <row>
     <entry>var</entry>
     <entry>numeric</entry>
     <entry>Yes</entry>
     <entry><emphasis>n/a</emphasis></entry>
     <entry>equation variable value</entry>
    </row>
    <row>
     <entry>assign</entry>
     <entry>string</entry>
     <entry>No</entry>
     <entry><emphasis>n/a</emphasis></entry>
     <entry>template variable the output will be assigned to</entry>
    </row>
    <row>
     <entry>[var ...]</entry>
     <entry>numeric</entry>
     <entry>Yes</entry>
     <entry><emphasis>n/a</emphasis></entry>
     <entry>equation variable value</entry>
    </row>
   </tbody>
  </tgroup>
 </informaltable>

 <note>
  <title>Technical Note</title>
  <para>
   {math} is an expensive function in performance due to its use of the php
   <ulink url="&url.php-manual;eval">eval()</ulink> function. Doing the math in PHP is much
   more
   efficient, so whenever possible do the math calculations in PHP
   and <link linkend="api.assign">assign()</link>
   the results to the template. Definately avoid
   repetitive {math} function calls, eg within
   <link linkend="language.function.section">{section}</link> loops.
  </para>
 </note>
 <example>
  <title>{math}</title>
  <para>
  <emphasis role="bold">Example a:</emphasis>
  </para>
  <programlisting>
<![CDATA[
   {* $height=4, $width=5 *}

   {math equation="x + y" x=$height y=$width}
]]>
  </programlisting>
  <para>
   The above example will output:
  </para>
  <screen>
<![CDATA[
   9
]]>
  </screen>
  <para>
    <emphasis role="bold">Example b:</emphasis>
  </para>
  <programlisting>
<![CDATA[
   {* $row_height = 10, $row_width = 20, #col_div# = 2, assigned in template *}

   {math equation="height * width / division"
   height=$row_height
   width=$row_width
   division=#col_div#}
]]>
  </programlisting>
  <para>
   The above example will output:
  </para>
  <screen>
<![CDATA[
   100
]]>
  </screen>
  <para>
  <emphasis role="bold">Example c:</emphasis>
  </para>
  <programlisting>
<![CDATA[
   {* you can use parenthesis *}

   {math equation="(( x + y ) / z )" x=2 y=10 z=2}
]]>
  </programlisting>
  <para>
   The above example will output:
  </para>
  <screen>
<![CDATA[
   6
]]>
  </screen>
    <para>
    <emphasis role="bold">Example d:</emphasis>
  </para>
  <programlisting>
<![CDATA[
   {* you can supply a format parameter in sprintf format *}

   {math equation="x + y" x=4.4444 y=5.0000 format="%.2f"}
   ]]>
  </programlisting>
  <para>
   The above example will output:
  </para>
  <screen>
<![CDATA[
   9.44
]]>
  </screen>
 </example>
</sect1>
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