code: public static final BitVector fromBigInteger(BigInteger bigInt) {
  		if (bigInt == null) throw new IllegalArgumentException();
  		final int length = bigInt.bitLength();
  		return fromBigIntegerImpl(bigInt, length);
  	}
docs: Creates a {@link BitVector} from a <code>BigInteger</code>. The bits of
  the integer copied into the new bit vector. The size of the returned
  {@link BitVector} is <code>bigInt.bitLength()</code>. Negative values are
  recorded using 2's complement encoding. No sign-bit is included in the
  returned {@link BitVector}.
  
  @param bigInt
  a big integer
  @return a {@link BitVector} initialized with the bits of the big integer
  @see #fromBigInteger(BigInteger, int)
  @see Bits#asStore(BigInteger)