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                <li class="toctree-l3"><a href="#general">General</a></li>
                
                    <li><a class="toctree-l4" href="#wrap-functions">Wrap functions</a></li>
                
                    <li><a class="toctree-l4" href="#wrap-methods-and-fields">Wrap methods and fields</a></li>
                
            
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                <h1 id="general">General</h1>
<p>Luwra provides an easy way to turn any C or C++ function into a
<a href="http://www.lua.org/manual/5.3/manual.html#lua_CFunction">lua_CFunction</a> which can be used by the
Lua VM. Note, all parameter types must be readable from the stack (<code>Value&lt;T&gt;::read</code> exists for all)
and the return type must be pushable (<code>Value&lt;T&gt;::push</code> exists).</p>
<h2 id="wrap-functions">Wrap functions</h2>
<p>Assuming you have a function similiar to this:</p>
<pre><code class="c++">int my_function(const char* a, int b) {
    return /* magic */;
}
</code></pre>

<p>You can easily wrap it using the <code>LUWRA_WRAP</code> macro:</p>
<pre><code class="c++">// Convert to lua_CFunction
lua_CFunction cfun = LUWRA_WRAP(my_function);

// Do something with it, for example set it as a Lua global function
luwra::setGlobal(lua, &quot;my_function&quot;, cfun);
</code></pre>

<p><strong>Note:</strong> Do not provide the address of your function (e.g. <code>&amp;my_function</code>) to any wrapping macro.
The macros will take care of this themselves. You must provide only the name of the function.</p>
<p>Calling the function from Lua is fairly straightforward:</p>
<pre><code class="lua">local my_result = my_function(&quot;Hello World&quot;, 1337)
print(my_result)
</code></pre>

<h2 id="wrap-methods-and-fields">Wrap methods and fields</h2>
<p>It is also possible to turn C++ field accessors and methods into <code>lua_CFunction</code>s. It is a little
trickier than wrapping normal functions. The resulting Lua functions expect the first (or <code>self</code>)
parameter to be a user type instance of the type which the wrapped field or method belongs to.</p>
<p><strong>Note:</strong> Before you wrap fields and methods manually, you might want to take a look at the
<a href="../user-types/">User Types</a> section.</p>
<p>The next examples will operate on the following structure:</p>
<pre><code class="c++">struct Point {
    double x, y;

    // ...

    void scale(double f) {
        x *= f;
        y *= f;
    }
};
</code></pre>

<p>In order to wrap <code>x</code>, <code>y</code> and <code>scale</code> we utilize the <code>LUWRA_WRAP</code> macro again:</p>
<pre><code class="c++">lua_CFunction cfun_x     = LUWRA_WRAP(Point::x),
              cfun_y     = LUWRA_WRAP(Point::y),
              cfun_scale = LUWRA_WRAP(Point::scale);

// Register as globals
luwra::setGlobal(lua, &quot;x&quot;, cfun_x);
luwra::setGlobal(lua, &quot;y&quot;, cfun_y);
luwra::setGlobal(lua, &quot;scale&quot;, cfun_scale);
</code></pre>

<p>Usage looks like this:</p>
<pre><code class="lua">local my_point = -- Magic

-- Access 'x' and 'y' field
print(x(my_point), y(my_point))

-- Set 'x' and 'y' field
x(my_point, 13.37)
y(my_point, 73.31)

-- Invoke 'scale' method
scale(my_point, 2)
</code></pre>
              
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