GNU R class for vectors of 1-bit booleans

 This GNU R package provides bitmapped vectors of booleans (no NAs),
 coercion from and to logicals, integers and integer subscripts; fast
 boolean operators and fast summary statistics. With 'bit' vectors you
 can store true binary booleans {FALSE,TRUE} at the expense of 1 bit
 only, on a 32 bit architecture this means factor 32 less RAM and ~
 factor 32 more speed on boolean operations. Due to overhead of R calls,
 actual speed gain depends on the size of the vector: expect gains for
 vectors of size > 10000 elements. Even for one-time boolean operations
 it can pay-off to convert to bit, the pay-off is obvious, when such
 components are used more than once.
 .
 Reading from and writing to bit is approximately as fast as accessing
 standard logicals - mostly due to R's time for memory allocation. The
 package allows one to work with pre-allocated memory for return values
 by calling .Call() directly: when evaluating the speed of C-access with
 pre-allocated vector memory, coping from bit to logical requires only
 70% of the time for copying from logical to logical; and copying from
 logical to bit comes at a performance penalty of 150%. the package now
 contains further classes for representing logical selections: 'bitwhich'
 for very skewed selections and 'ri' for selecting ranges of values for
 chunked processing. All three index classes can be used for subsetting
 'ff' objects (ff-2.1-0 and higher).