View Compilation Error

0_0_34939417_24217.cpp: In function 'int main()':
0_0_34939417_24217.cpp:16:42: error: 'is_fxiji' was not declared in this scope
                 if(is_fxiji(seg[i],seg[j]))
                                          ^
0_0_34939417_24217.cpp:17:46: error: 'is_inter' was not declared in this scope
                     if(is_inter(seg[i],seg[j])&&is_inter(seg[j],seg[i]))   //要分别对两直线进行跨立实验，才是两直线相交的充分必要条件
                                              ^