foo.cc: In constructor 'PolyList::PolyList(int)':
foo.cc:32:23: warning: unused variable 'tail' [-Wunused-variable]
   32 |                 Node *tail=NULL;
      |                       ^~~~
foo.cc: In member function 'void PolyList::Insert(Node*)':
foo.cc:47:20: error: 'p' was not declared in this scope
   47 |                 if(p!=NULL && p->data.index==newp->data.index  )
      |                    ^
foo.cc:57:40: error: type '<type error>' argument given to 'delete', expected pointer
   57 |                                 delete p;
      |                                        ^

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