Compilare: main.cpp: In function 'void fft(std::vector<std::complex<double> >&, bool)': main.cpp:23:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::complex<double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 23 | for(log2 = 0; (1 << log2) < y.size(); log2 ++); | ~~~~~~~~~~~~^~~~~~~~~~ main.cpp:25:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::complex<double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 25 | for(int i = 0; i < y.size(); i ++) { | ~~^~~~~~~~~~ main.cpp:30:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::complex<double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 30 | for(int len = 2; len <= y.size(); len <<= 1) { | ~~~~^~~~~~~~~~~ main.cpp:35:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::complex<double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 35 | for(int i = 0; i < y.size(); i += len) { | ~~^~~~~~~~~~ main.cpp:48:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::complex<double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 48 | for(int i = 0; i < y.size(); i ++) | ~~^~~~~~~~~~ main.cpp: In function 'void multiply(std::vector<std::complex<double> >&, std::vector<std::complex<double> >)': main.cpp:55:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::complex<double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 55 | for(size = 1; size < a.size() + b.size(); size *= 2); | ~~~~~^~~~~~~~~~~~~~~~~~~~~