(bitmatch (u8vector 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1)
 (((a double big) (b double big) (c boolean) (d boolean))
  (vector a b c d)))

Press ENTER or type command to continue
; outputs #(0.0 0.0 1 1)
(write (bitmatch (u8vector 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1)
         (((a double big) (b double big) (c 8) (d 8))
          (vector a b c d))))

; if we take the same thing but change c and d to booleans of 8 bits...
(write (bitmatch (u8vector 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1)
         (((a double big) (b double big) (c 8 boolean) (d 8 boolean))
          (vector a b c d))))
; ... we get Error: bitstring-malformed-pattern

; the documentation says that 8 bits should be the default, but if we remove them...
(write (bitmatch (u8vector 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1)
         (((a double big) (b double big) (c boolean) (d boolean))
          (vector a b c d))))
; ... we get Error: unbound variable: boolean