A bool-vector is a one-dimensional array whose elements must
be t or
The printed representation of a bool-vector is like a string, except
that it begins with ‘#&’ followed by the length. The string
constant that follows actually specifies the contents of the bool-vector
as a bitmap—each character in the string contains 8 bits, which
specify the next 8 elements of the bool-vector (1 stands for t,
and 0 for
nil). The least significant bits of the character
correspond to the lowest indices in the bool-vector.
(make-bool-vector 3 t) ⇒ #&3"^G" (make-bool-vector 3 nil) ⇒ #&3"^@"
These results make sense, because the binary code for ‘C-g’ is 111 and ‘C-@’ is the character with code 0.
If the length is not a multiple of 8, the printed representation shows extra elements, but these extras really make no difference. For instance, in the next example, the two bool-vectors are equal, because only the first 3 bits are used:
(equal #&3"\377" #&3"\007") ⇒ t