>> Except that this form makes a copy of the bignum, and for
	>> a 40k pile of bits that's pretty slow :-(.
	>
	>In this case, why not use an array of shorter integers?
	>
	>  def set_bit(vector, index)
	>    bucket = index & 63
	>    bit = index >> 6
	>    vector[bucket] |= 1 << bit
	>  end

Oh sure, I could.  I could also write my own hash functions,
etc.  It just seems like a basic enough facility to warrant
inclusion in the language, that's all (plus a small speed
advantage to coding it in C).

/\ndy