<dt><tt>!cast<type>(a)</tt></dt>
<dd>A symbol of type <em>type</em> obtained by looking up the string 'a' in
the symbol table. If the type of 'a' does not match <em>type</em>, TableGen
-aborts with an error. </dd>
+aborts with an error. !cast<string> is a special case in that the argument must
+be an object defined by a 'def' construct.</dd>
<dt><tt>!nameconcat<type>(a, b)</tt></dt>
<dd>Shorthand for !cast<type>(!strconcat(a, b))</dd>
<dt><tt>!subst(a, b, c)</tt></dt>
<dd>If 'a' and 'b' are of string type or are symbol references, substitute
'b' for 'a' in 'c.' This operation is analogous to $(subst) in GNU make.</dd>
-<dt><tt>!regmatch(a, b)</tt></dt>
- <dd>An integer {0,1} indicating whether string 'b' matched regular expression
-'a.'</dd>
<dt><tt>!foreach(a, b, c)</tt></dt>
<dd>For each member 'b' of dag or list 'a' apply operator 'c.' 'b' is a
dummy variable that should be declared as a member variable of an instantiated