/in/foo.c: In function 'main':
/in/foo.c:6:10: warning: format '%f' expects argument of type 'float *', but argument 2 has type 'double *' [-Wformat=]
  scanf("%f %f",&a,&b);
          ^
/in/foo.c:6:13: warning: format '%f' expects argument of type 'float *', but argument 3 has type 'double *' [-Wformat=]
  scanf("%f %f",&a,&b);
             ^