foo.cpp: In function 'std::istream& operator>>(std::istream&, num&)':
foo.cpp:41:31: error: 'reverse' was not declared in this scope
         reverse(c, c+strlen(c));
                               ^
foo.cpp: At global scope:
foo.cpp:45:8: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]
 } p("1"), q("1");
        ^
foo.cpp:45:16: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]
 } p("1"), q("1");
                ^