Compilare: user.cpp: In function ‘int main(int, const char**)’: user.cpp:36:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( hul.size() > aux && ccw( ptx[ hul[hul.size() - 2] ], ptx[ hul[hul.size() - 1] ], ptx[i] ) > 0 ) { ^ user.cpp:41:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( hul.size() > aux && ccw( ptx[ hul[hul.size() - 2] ], ptx[ hul[hul.size() - 1] ], ptx[i] ) > 0 ) { ^ user.cpp:46:61: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0, l = hul.size() - 1, r = 1; i < hul.size(); i ++, l = (l + 1) % hul.size(), r = (r + 1) % hul.size() ) { ^ user.cpp:50:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 2; i < hul.size(); i ++ ) { ^ user.cpp:55:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 2; i < hul.size(); i ++ ) { ^