/in/foo.c: In function 'qiujie':
/in/foo.c:22:25: error: 'realpart' undeclared (first use in this function)
   22 |                         realpart=-b/(2*a);
      |                         ^~~~~~~~
/in/foo.c:22:25: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:23:25: error: 'imagpart' undeclared (first use in this function)
   23 |                         imagpart=sqrt(-delta)/(2*a);
      |                         ^~~~~~~~