int degree(const symbol &s) const;
int ldegree(const symbol &s) const;
ex coeff(const symbol &s, int n=1) const;
int degree(const symbol &s) const;
int ldegree(const symbol &s) const;
ex coeff(const symbol &s, int n=1) const;
ex normal(lst &sym_lst, lst &repl_lst, int level=0) const;
ex subs(const lst & ls, const lst & lr) const;
protected:
ex normal(lst &sym_lst, lst &repl_lst, int level=0) const;
ex subs(const lst & ls, const lst & lr) const;
protected: