inline ex diff(ex const & thisex, symbol const & s, unsigned nth = 1)
{ return thisex.diff(s, nth); }
+inline ex series(ex const & thisex, symbol const & s, ex const & point, int order = 6)
+{ return thisex.series(s, point, order); }
+
inline ex subs(ex const & thisex, ex const & e)
{ return thisex.subs(e); }