ex to_rational(lst &repl_lst) const;
bool match(const ex & pattern, lst & repl_lst) const;
ex subs(const lst & ls, const lst & lr, bool no_pattern = false) const;
protected:
ex to_rational(lst &repl_lst) const;
bool match(const ex & pattern, lst & repl_lst) const;
ex subs(const lst & ls, const lst & lr, bool no_pattern = false) const;
protected: