foo.cpp: In function 'bool is_dian(std::string)':
foo.cpp:10:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.length();i++)
                         ^
foo.cpp: In function 'bool work(std::string)':
foo.cpp:33:33: error: 'puts' was not declared in this scope
          puts((haha+now).c_str());
                                 ^
foo.cpp: In function 'bool is_dian(std::string)':
foo.cpp:15:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^