/*
 *  call-seq:
 *     bv.hash -> int
 *  
 *  Used to store bit vectors in Hashes. Especially useful if you want to
 *  cache them.
 */
VALUE
frt_bv_hash(VALUE self)
{
    BitVector *bv;
    GET_BV(bv, self);
    return LONG2NUM(bv_hash(bv));
}