opcodes/ifndef.xml


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<refentry id="ifndef">
<indexterm id="IndexIfndefOrch"><primary>&num;ifndef</primary><secondary>orchestra</secondary></indexterm>

<indexterm id="IndexIfndef"><primary>&num;ifndef</primary></indexterm>
  <refentryinfo><title>Orchestra Syntax:Macros</title></refentryinfo>
  <refmeta>
    <refentrytitle>&num;ifndef</refentrytitle>
  </refmeta>


  <refnamediv>
    <refname>&num;ifndef</refname>

    <refpurpose>
      Conditional reading of code.
                </refpurpose>
  </refnamediv>
 
  <refsect1>
    <title>Description</title>
    <para>
      If the specified macro is not defined then <emphasis>&num;ifndef</emphasis> can
    incorporate text into an orchestra upto the next
    <emphasis>&num;end</emphasis>.  
    This is similar to, but independent of, the <link
    linkend="ScoreMacros"><citetitle>macro system in the score
    language</citetitle></link>.
    </para>

  </refsect1>
 
  <refsect1>
    <title>Syntax</title>
    <synopsis><command>&num;ifndef</command> NAME</synopsis>
    <synopsis>....</synopsis>
    <synopsis><command>&num;else</command>&#160;</synopsis>
    <synopsis>....</synopsis>
    <synopsis><command>&num;end</command>&#160;</synopsis>
  </refsect1>

  <refsect1>
    <title>Performance</title>
    <para>
      Note that the <emphasis>&num;ifndef</emphasis> can be nested, like in the C preprocessor language.
    </para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <link linkend="dollar"><citetitle>&dollar;NAME</citetitle></link>, 
      <link linkend="define"><citetitle>&num;define</citetitle></link>,
      <link linkend="ifdef"><citetitle>&num;ifdef</citetitle></link>.
    </para>
  </refsect1>
 
  <refsect1>
    <title>Credits</title>
    <para>
      <simplelist>
        <member>Author: &namejohn;</member>
        <member>University of Bath/Codemist Ltd.</member>
        <member>Bath, UK</member>
        <member>April 2005</member>
      </simplelist>
    </para>

    <para>New in Csound5 (and 4.23f13)</para>
  </refsect1>
</refentry>