position (ANSI and GNU Common Lisp Document)

Next: search, Previous: find, Up: Sequences Dictionary

#### 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.

Next: search, Previous: find, Up: Sequences Dictionary