foo.cc: In member function 'void Num::outfile()':
foo.cc:32:8: warning: statement has no effect [-Wunused-value]
   32 |   for (j;j>=i;j--){
      |        ^
foo.cc: In member function 'Num& Num::operator*(Num)':
foo.cc:39:7: warning: unused variable 'i' [-Wunused-variable]
   39 |   int i;
      |       ^
foo.cc: In function 'void work()':
foo.cc:63:11: warning: 'ch' is used uninitialized in this function [-Wuninitialized]
   63 |  while (ch!=EOF){
      |           ^

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