<p>
The function <code>Slice</code> returns a slice whose underlying array starts at <code>ptr</code>
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,