/in/foo.cc: In function 'double ri(char)':
/in/foo.cc:16:1: warning: control reaches end of non-void function [-Wreturn-type]
 } 
 ^
/in/foo.cc: In function 'double suan(double, char, double)':
/in/foo.cc:24:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^