View Compilation Error

0_0_29119950_27126.cpp: In function 'double dis(pt, pt)':
0_0_29119950_27126.cpp:29:61: error: expected primary-expression before '.' token
      return (a.x - b.x) * (a.x - b.x) + (a.y- b.y) * (a.y - .b.y);
                                                             ^