Compute the Hamming Weight of a word.
function weight(word) {

  return HAMMING_TABLE[ (word >> 0x00) & 0xF ] +
         HAMMING_TABLE[ (word >> 0x04) & 0xF ] +
         HAMMING_TABLE[ (word >> 0x08) & 0xF ] +
         HAMMING_TABLE[ (word >> 0x0C) & 0xF ] +
         HAMMING_TABLE[ (word >> 0x10) & 0xF ] +
         HAMMING_TABLE[ (word >> 0x14) & 0xF ] +
         HAMMING_TABLE[ (word >> 0x18) & 0xF ] +
         HAMMING_TABLE[ (word >> 0x1C) & 0xF ];

}