void print(ostream & os, unsigned upper_precedence=0) const;
void printtree(ostream & os, unsigned indent) const;
bool info(unsigned inf) const;
void print(ostream & os, unsigned upper_precedence=0) const;
void printtree(ostream & os, unsigned indent) const;
bool info(unsigned inf) const;
ex & let_op(int const i);
ex expand(unsigned options=0) const;
bool has(ex const & other) const;
ex & let_op(int const i);
ex expand(unsigned options=0) const;
bool has(ex const & other) const;