Compilare: user.cpp: In function ‘void lire(std::vector<std::vector<double> >&)’: user.cpp:6:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] #define xs x.size() ^ user.cpp:20:21: note: in expansion of macro ‘xs’ for (int i=0; i<xs; i++) ^ user.cpp:23:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0; j<x[i].size(); j++) ^ user.cpp: In function ‘void direct(std::vector<std::vector<double> >&)’: user.cpp:33:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<xs-1; i++) ^ user.cpp:6:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] #define xs x.size() ^ user.cpp:38:31: note: in expansion of macro ‘xs’ for (int j=i+1; j<xs; j++) ^ user.cpp:6:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] #define xs x.size() ^ user.cpp:44:27: note: in expansion of macro ‘xs’ for (int j=i+1; j<xs; j++) ^ user.cpp:47:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (k=i; k<xs+1; k++) ^ user.cpp: In function ‘void invers(std::vector<double>&)’: user.cpp:61:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=i+1; j<a[0].size(); j++) ^ user.cpp: At global scope: user.cpp:69:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main() ^