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(elisp)Bool-Vectors

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Bool-vectors
============

   A bool-vector is much like a vector, except that it stores only the
values `t' and `nil'.  If you try to store any non-`nil' value into an
element of the bool-vector, the effect is to store `t' there.  As with
all arrays, bool-vector indices start from 0, and the length cannot be
changed once the bool-vector is created.  Bool-vectors are constants
when evaluated.

   There are two special functions for working with bool-vectors; aside
from that, you manipulate them with same functions used for other kinds
of arrays.

 - Function: make-bool-vector length initial
     Return a new bool-vector of LENGTH elements, each one initialized
     to INITIAL.

 - Function: bool-vector-p object
     This returns `t' if OBJECT is a bool-vector, and `nil' otherwise.

   Here is an example of creating, examining, and updating a
bool-vector.  Note that the printed form represents up to 8 boolean
values as a single character.

     (setq bv (make-bool-vector 5 t))
          => #&5"^_"
     (aref bv 1)
          => t
     (aset bv 3 nil)
          => nil
     bv
          => #&5"^W"

These results make sense because the binary codes for control-_ and
control-W are 11111 and 10111, respectively.