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<refentry id="lua_exec">
<indexterm id="Indexlua_exec">
<primary>
lua_exec
</primary>
</indexterm>
<refentryinfo><title>Lua Opcodes</title></refentryinfo>
<refmeta>
<refentrytitle>
lua_exec
</refentrytitle>
</refmeta>
<refnamediv>
<refname>
lua_exec
</refname>
<refpurpose>
Executes an arbitrary block of Lua code from the Csound orchestra.
</refpurpose>
</refnamediv>
<refsect1>
<title>
Description
</title>
<para>
Executes an arbitrary block of Lua code from the Csound orchestra.
The code is executed at initialization time, typically from the
orchestra header.
</para>
</refsect1>
<refsect1>
<title>
Syntax
</title>
<synopsis><command>lua_exec</command> Sluacode</synopsis>
</refsect1>
<refsect1>
<title>
Initialization
</title>
<para>
<emphasis>Sluacode</emphasis> -- A block of Lua code, of any
length. Multi-line blocks may be enclosed in
double braces (i.e. <literal>{{ }}</literal>). This code is
evaluated once at initialization time, typically from the
orchestra header. Global and local variables, functions,
tables, and classes may be declared and defined. Objects defined
at global Lua scope remain in scope throughout the performance,
and are visible to any other Lua code in the same Csound thread.
</para>
<para>
The running instance of Csound is stored as a
Lua lightuserdata in a global variable <literal>csound</literal>.
This can be passed to any Csound API function. One use of this
would be to generate a score using Lua in the orchestra header,
and schedule the events for performance using <literal>csoundInputMessage</literal>.
</para>
<note>
<para>
By default, all objects defined in Lua are defined at global
scope. In order to ensure that objects are confined to their
own block of code, that is to ensure that the object is visible
only in lexical scope, the object must be declared as local.
This is the feature of Lua that beginners tend to find the most
troublesome.
</para>
<para>
Another thing to look out for is that Lua arrays use 1-based
indexing, not the 0-based indexing used in C and many other
programming languages.
</para>
</note>
</refsect1>
<refsect1>
<title>
See Also
</title>
<para>
<link linkend="lua_opdef"><citetitle>lua_opdef</citetitle></link>,
<link linkend="lua_opcall"><citetitle>lua_opcall</citetitle></link>.
</para>
</refsect1>
<refsect1>
<title>
Credits
</title>
<para>
By: &namemichael; 2011
</para>
<para>
New in Csound version 5.13.2
</para>
</refsect1>
</refentry>
|
