foo.cc: In function 'int main()':
foo.cc:10:14: error: expected unqualified-id before '<<' token
   10 |         std::<<"十进制："<<dec<<"，二进制："<<conv_dec_to_bin(dec)<<std::endl
      |              ^~
foo.cc:10:47: error: 'conv_dec_to_bin' was not declared in this scope
   10 |         std::<<"十进制："<<dec<<"，二进制："<<conv_dec_to_bin(dec)<<std::endl
      |                                               ^~~~~~~~~~~~~~~
foo.cc:5:9: warning: unused variable 'bin' [-Wunused-variable]
    5 |     int bin=0;
      |         ^~~

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