title: Expected unqualified-id before 'xor' token
body: <p>Why the g++ compiler says: error: expected unqualified-id before 'xor' token</p>
  
  <pre><code>class BigInteger{
  public:
      unsigned *array;
  
      BigInteger xor(BigInteger bi){    // g++ indicates error this line
          BigInteger n;
          if(bi.array == (unsigned*)0){
              return n;
          }
          return n;
      }
  };
  </code></pre>