Compilare: main.cpp: In member function 'void Expression::bkt(int)': main.cpp:75:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (p + 1 == lett.size()) { ~~~~~~^~~~~~~~~~~~~~ main.cpp: In member function 'int Expression::solutions()': main.cpp:99:13: warning: unused variable 'ret' [-Wunused-variable] int ret(0) ; ^~~ main.cpp:110:13: warning: unused variable 'i' [-Wunused-variable] int i ; ^ main.cpp: In function 'int main()': main.cpp:122:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("artifact.in", "r", stdin) ; ^ main.cpp:123:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("artifact.out", "w", stdout) ; ^