Some Scheme implementations (including Guile and Kawa) have bit vectors.
So does Common Lisp.  Does any Scheme have u1vectors?

A bitvector and a u1vector are "equivalent" except that the former stores
#f/#t while the latter stores exact integers 0/1; however, the low-level
data structures (and performance issues) are the same.  I don't know
which of bitvector or u1vector is a priori more useful, elegant,
or "mathematically" consistent.  However, given existing art for bitvectors
adding u1vectors seems to have limited benefit.  I suggest instead
standardizing bitvector.
--
	--Per Bothner
xxxxxx@bothner.com   http://per.bothner.com/