foo.cpp: In function 'bool compare3(num, num)':
foo.cpp:77:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(int i=a.len;i>=1;i--)
  ^~~
foo.cpp:79:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   return 1;
   ^~~~~~
foo.cpp: In function 'num operator*(num, num)':
foo.cpp:51:17: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized]
    t.data[t.len]=y;
    ~~~~~~~~~~~~~^~