count (ANSI and GNU Common Lisp Document)

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#### 17.3.10 count, count-if, count-if-not [Function]

`count` item sequence &key from-end start end key test test-not ⇒ n

`count-if` predicate sequence &key from-end start end key ⇒ n

`count-if-not` predicate sequence &key from-end start end key ⇒ n

#### Arguments and Values::

item—an object.

sequence—a proper sequence.

predicate—a designator for a function of one argument that returns a generalized boolean.

from-end—a generalized boolean. The default is false.

test—a designator for a function of two arguments that returns a generalized boolean.

test-not—a designator for a function of two arguments that returns a generalized boolean.

start, end—bounding index designators of sequence. The defaults for start and end are `0` and nil, respectively.

key—a designator for a function of one argument, or nil.

n—a non-negative integer less than or equal to the length of sequence.

#### Description::

count, count-if, and count-if-not count and return the number of elements in the sequence bounded by start and end that satisfy the test.

The from-end has no direct effect on the result. However, if from-end is true, the elements of sequence will be supplied as arguments to the test, test-not, and key in reverse order, which may change the side-effects, if any, of those functions.

#### Examples::

     (count #\a "how many A's are there in here?") ⇒  2
     (count-if-not #'oddp '((1) (2) (3) (4)) :key #'car) ⇒  2
     (count-if #'upper-case-p "The Crying of Lot 49" :start 4) ⇒  2

#### Exceptional Situations::

Should be prepared to signal an error of type type-error if sequence is not a proper sequence.

#### See Also::

Rules about Test Functions,

Traversal Rules and Side Effects

#### Notes::

The `:test-not` argument is deprecated.

The function count-if-not is deprecated.

Next: length, Previous: reduce, Up: Sequences Dictionary