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<pre class=code>
<B><FONT COLOR="#0000FF">signature</FONT></B> MLTON_WEAK =
   <B><FONT COLOR="#0000FF">sig</FONT></B>
      <B><FONT COLOR="#A020F0">type</FONT></B><B><FONT COLOR="#228B22"> 'a t

      </FONT></B><B><FONT COLOR="#A020F0">val</FONT></B> get: 'a t -&gt; 'a option
      <B><FONT COLOR="#A020F0">val</FONT></B> new: 'a -&gt; 'a t
   <B><FONT COLOR="#0000FF">end</FONT></B>
</PRE>
<p>
 
</p>
<p>
A weak pointer is a pointer to an object that is nulled if the object becomes <a href="Reachability">unreachable</a> due to garbage collection.  The weak pointer does not itself cause the object it points to be retained by the garbage collector -- only other strong pointers can do that. For objects that are not allocated in the heap, like integers, a weak pointer will always be nulled.  So, if <tt>w:&nbsp;int&nbsp;Weak.t</tt> then <tt>Weak.get&nbsp;w&nbsp;=&nbsp;NONE</tt>. 
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    <li>
<p>
 <tt>type&nbsp;'a&nbsp;t</tt>  <br>
the type of weak pointers to objects of type <tt>'a</tt> 
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    <li class="gap">
<p>
 <tt>get&nbsp;w</tt>  <br>
returns <tt>NONE</tt> if the object pointed to by <tt>w</tt> no longer  exists.  Otherwise, returns <tt>SOME</tt> of the object pointed to by  <tt>w</tt>. 
</p>
</li>
    <li class="gap">
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 <tt>new&nbsp;x</tt>  <br>
returns a weak pointer to <tt>x</tt>. 
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Last edited on 2007-08-23 03:45:54 by <span title="c-71-57-91-146.hsd1.il.comcast.net"><a href="MatthewFluet">MatthewFluet</a></span>.
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