/in/foo.cc: In function 'bool operator<(P, P)':
/in/foo.cc:21:28: error: expected primary-expression before '<' token
 bool operator <(P p, P q) {<span style="white-space:pre">  //如果p1^p2 〉0，说明p1经逆时针旋转<180度可以到p2，则 p1 </span><<span style="white-space:pre"> p2</span>
                            ^
/in/foo.cc:21:29: error: 'span' was not declared in this scope
 bool operator <(P p, P q) {<span style="white-space:pre">  //如果p1^p2 〉0，说明p1经逆时针旋转<180度可以到p2，则 p1 </span><<span style="white-space:pre"> p2</span>
                             ^~~~
/in/foo.cc:24:5: error: 'else' without a previous 'if'
     else return true;
     ^~~~