Let's say i have a hierarchy of object that all inherits from a abse class
called base_impl.<br />Among those classes, most of them are tempalte that
have large, complex type.<br /><br />My idea was to use boost::any to
store any of this classes' instances, any_cast them back to base_impl* and
call one of the base_impl virtual method.<br /><br />Basically I did this
:<br /><br />&nbsp; struct expression_impl<br />&nbsp; {<br
/>&nbsp;&nbsp;&nbsp; virtual ~expression_impl() {}<br />&nbsp;&nbsp;&nbsp;
virtual void evaluate() const = 0;<br />&nbsp; };<br /><br />&nbsp; struct
expression<br />&nbsp; {<br />&nbsp;&nbsp;&nbsp; template&lt;class T&gt;
expression( T const&amp; x ) : mExpr(x) {}<br /><br />&nbsp;&nbsp;&nbsp;
void evaluate() {
boost::any_cast&lt;expression_impl*&gt;(mExpr)-&gt;evaluate(); }<br
/>&nbsp;&nbsp;&nbsp; boost::any mExpr;<br />&nbsp; };<br /><br />Alas this
fails in a bad_any_cast exception. Considering that the basic use case of
expression is :<br /><br />expression e =
/some_function_making_emporary_base_impl_instance();<br /><br />I can't
rely on stroing a pointer in the boost::any member.<br />Any solution to
this problem or am I doing something wrong.