File r37/lisp/csl/html/r37_0037.html from the latest check-in
<A NAME=tilde> <TITLE>tilde</TITLE></A> <b><a href=r37_idx.html>INDEX</a></b><p><p> <B>~</B> _ _ _ <B>TILDE</B> _ _ _ _ _ _ _ _ _ _ _ _ <B>operator</B><P> <P> The <em>~</em> is used as a unary prefix operator in the left-hand sides of <A HREF=r37_0060.html>rule</A>s to mark <A HREF=r37_0061.html>free variable</A>s. A double tilde marks an optional <A HREF=r37_0061.html>free variable</A>. <P> <P>