not reloading local variables from shared memory.
For example, a compiler must not discard <code>i</code> and reload it
a second time from <code>*p</code> in this program:
</p>

<pre>
i := *p
if i &lt; 0 || i &gt;= len(funcs) {
	panic("invalid function index")
}
... complex code ...
// compiler must NOT reload i = *p here
funcs[i]()
</pre>

<p>

and whose length and capacity are <code>len</code>.
<code>Slice(ptr, len)</code> is equivalent to
</p>

<pre>
(*[len]ArbitraryType)(unsafe.Pointer(ptr))[:]
</pre>

<p>
except that, as a special case, if <code>ptr</code>
is <code>nil</code> and <code>len</code> is zero,
<code>Slice</code> returns <code>nil</code>.
</p>

<p>

<p>
Given the declarations
</p>
<pre>
type Point3D struct { x, y, z float64 }
type Line struct { p, q Point3D }
</pre>

<p>
one may write
</p>

<pre>
origin := Point3D{}                            // zero value for Point3D
line := Line{origin, Point3D{y: -4, z: 12.3}}  // zero value for line.q.x
</pre>

<p>
For array and slice literals the following rules apply:
</p>
<ul>