foo.cc: In function 'std::string InToPost(std::string)':
foo.cc:20:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |         for(int i=0;i<s.size();i++)
      |                     ~^~~~~~~~~
foo.cc:33:34: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |                         while(i+1<s.size()&&isdigit(s[i+1]))
      |                               ~~~^~~~~~~~~
foo.cc:32:46: warning: variable 'f' set but not used [-Wunused-but-set-variable]
   32 |                         ret.push_back(c);int f=0;
      |                                              ^
foo.cc: In function 'double js(double, char, double)':
foo.cc:13:1: warning: control reaches end of non-void function [-Wreturn-type]
   13 | }
      | ^

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