Syntax:
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
Side Effects: None.
Affected By: None.
Exceptional Situations:
Should be prepared to signal an error of type type-error if sequence is not a proper sequence.
See Also:
find, Section 3.6 (Traversal Rules and Side Effects)
Notes:
The :test-not argument is deprecated.
The function position-if-not is deprecated.
The following X3J13 cleanup issues, not part of the specification, apply to this section:RetroSearch is an open source project built by @garambo | Open a GitHub Issue
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