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  ANSI Common Lisp   17 Sequences   17.3 Dictionary of Sequences

17.3.10 count, count-if, count-if-not Function

Syntax:
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:
Section 17.2 Rules about Test Functions, Section 3.6 Traversal Rules and Side Effects

Notes:
The :test-not argument is deprecated.

The function count-if-not is deprecated.

Allegro CL Implementation Details:
None.

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