/in/foo.cc: In function 'int main()':
/in/foo.cc:18:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<str.length();i++)
              ~^~~~~~~~~~~~~
/in/foo.cc:47:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<oper.length();i++)
              ~^~~~~~~~~~~~~~
/in/foo.cc:72:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<oper.length();i++)
              ~^~~~~~~~~~~~~~
/in/foo.cc:91:23: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized]
    num[x]=num[x]+num[y];
                       ^
/in/foo.cc:91:16: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
    num[x]=num[x]+num[y];
                ^