Department;
of;
Mathematical;
Sciences,;
Tsinghua;
University,;
Beijing;
100084,;
China;
State;
Key;
Laboratory;
of;
Information;
Security,;
Graduate;
School;
of;
Chinese;
Academy;
of;
Sciences,;
Beijing;
100039,;
China;
Department;
of;
Mathematical;
Sciences,;
Tsinghua;
University,;
Beijing;
100084,;
China;
algebraic; function; field,; quadratic; function; field,; ideal; class; group,; ideal; class; number,continued; fraction; of; function.;