View Compilation Error

0_0_23444365_5002.cpp: In function 'db cal2(P&, P&, P&)':
0_0_23444365_5002.cpp:43:18: error: invalid initialization of non-const reference of type 'V&' from an rvalue of type 'V'
  double tmp1=dc(a>>b,a>>c),tmp2=dc(b>>a,b>>c);
                  ^
0_0_23444365_5002.cpp:40:4: note: in passing argument 1 of 'db dc(V&, V&)'
 db dc(V &a,V &b){return a.x*b.x+a.y*b.y;}
    ^
0_0_23444365_5002.cpp:44:13: error: 'tmp2' was not declared in this scope
  if(tmp1>0&&tmp2>0)return fabs((a>>b)*(a>>c))/dis(a,b);
             ^