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