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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 -> 'a option
<B><FONT COLOR="#A020F0">val</FONT></B> new: 'a -> 'a t
<B><FONT COLOR="#0000FF">end</FONT></B>
</PRE>
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<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: int Weak.t</tt> then <tt>Weak.get w = NONE</tt>.
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<tt>type 'a t</tt> <br>
the type of weak pointers to objects of type <tt>'a</tt>
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<tt>get 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>.
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<tt>new 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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