ex eval(int level=0) const;
ex evalf(int level=0) const;
ex normal(lst &sym_lst, lst &repl_lst, int level=0) const;
ex eval(int level=0) const;
ex evalf(int level=0) const;
ex normal(lst &sym_lst, lst &repl_lst, int level=0) const;
ex subs(const lst & ls, const lst & lr) const;
protected:
ex derivative(const symbol & s) const;
ex subs(const lst & ls, const lst & lr) const;
protected:
ex derivative(const symbol & s) const;