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>
   <varname>{math}</varname> allows the template designer to do math equations
   in the template.
   </para>
   <itemizedlist>
   <listitem><para>
   Any numeric template variables may be used in the
   equations, and the result is printed in place of the tag.
   </para></listitem>

   <listitem><para>
   The variables used in the equation are passed as parameters,
   which can  be template variables or static values.
   </para></listitem>

   <listitem><para>+, -, /, *, 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
   <ulink url="&url.php-manual;eval">math</ulink> functions.
  </para></listitem>

  <listitem><para>
   If you supply the <parameter>assign</parameter> attribute, the output of the
   <varname>{math}</varname> function will be assigned to this template
   variable instead of  being output to the template.
   </para></listitem>
  </itemizedlist>

   <note>
  <title>Technical Note</title>
  <para>
   <varname>{math}</varname> is an expensive function in performance due to
   its use of the php <ulink url="&url.php-manual;eval">
   <varname>eval()</varname></ulink> function. Doing the math in PHP is much
   more  efficient, so whenever possible do the math calculations in the script
   and <link linkend="api.assign"><varname>assign()</varname></link>
   the results to the template. Definitely avoid  repetitive
   <varname>{math}</varname> function calls, eg within
    <link linkend="language.function.section">
    <varname>{section}</varname></link> loops.
  </para>
 </note>

 <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>


 <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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