17.3.15 position, position-if, position-if-not [Function]

position item sequence &key from-end test test-not start end key ⇒ position

position-if predicate sequence &key from-end start end key ⇒ position

position-if-not predicate sequence &key from-end start end key ⇒ position

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.

position—a bounding index of sequence, or nil.

Description::

position, position-if, and position-if-not each search sequence for an element that satisfies the test.

The position returned is the index within sequence of the leftmost (if from-end is true) or of the rightmost (if from-end is false) element that satisfies the test; otherwise nil is returned. The index returned is relative to the left-hand end of the entire sequence, regardless of the value of start, end, or from-end.

Examples::

 (position #\a "baobab" :from-end t) ⇒  4
 (position-if #'oddp '((1) (2) (3) (4)) :start 1 :key #'car) ⇒  2
 (position 595 '()) ⇒  NIL
 (position-if-not #'integerp '(1 2 3 4 5.0)) ⇒  4 

Exceptional Situations::

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

See Also::

find ,

Traversal Rules and Side Effects

Notes::

The :test-not argument is deprecated.

The function position-if-not is deprecated.