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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.

There are also some bool-vector set operation functions, described below:

- Function:
**bool-vector-exclusive-or***a b &optional c* Return

*bitwise exclusive or*of bool vectors`a`and`b`. If optional argument`c`is given, the result of this operation is stored into`c`. All arguments should be bool vectors of the same length.

- Function:
**bool-vector-union***a b &optional c* Return

*bitwise or*of bool vectors`a`and`b`. If optional argument`c`is given, the result of this operation is stored into`c`. All arguments should be bool vectors of the same length.

- Function:
**bool-vector-intersection***a b &optional c* Return

*bitwise and*of bool vectors`a`and`b`. If optional argument`c`is given, the result of this operation is stored into`c`. All arguments should be bool vectors of the same length.

- Function:
**bool-vector-set-difference***a b &optional c* Return

*set difference*of bool vectors`a`and`b`. If optional argument`c`is given, the result of this operation is stored into`c`. All arguments should be bool vectors of the same length.

- Function:
**bool-vector-not***a &optional b* Return

*set complement*of bool vector`a`. If optional argument`b`is given, the result of this operation is stored into`b`. All arguments should be bool vectors of the same length.

- Function:
**bool-vector-subsetp***a b* Return

`t`

if every`t`

value in`a`is also t in`b`,`nil`

otherwise. All arguments should be bool vectors of the same length.

- Function:
**bool-vector-count-consecutive***a b i* Return the number of consecutive elements in

`a`equal`b`starting at`i`.`a`

is a bool vector,`b`is`t`

or`nil`

, and`i`is an index into`a`

.

- Function:
**bool-vector-count-population***a* Return the number of elements that are

`t`

in bool vector`a`.

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.

Next: Rings, Previous: Char-Tables, Up: Sequences Arrays Vectors [Contents][Index]