Simplified Common Lisp reference
find
Symbol class: Sequences (Lists, Strings) and Arrays
Syntax:
Symbol type: function
finditemsequencetest(keyword)from-end(keyword)start(keyword)end(keyword)key(keyword) => element
Argument description:
item an item to be found
sequence a sequence to be searched
test function key and item comparison
from-end direction of search, default is NIL - forward
start starting position for search, default is 0
end final position for search, default is NIL - end of sequence
key function for extracting value before test

FIND function searches for an element (item) satisfying the test. Return value is element itself or NIL if item is not found. See also POSITION, POSITION-IF, FIND, FIND-IF and MEMBER.

(find #\s "Some sequence") => #\s
(find #\s "Some sequence" :key #'char-downcase) => #\S
(find #\s "Some sequence" :key #'char-downcase :start 1) => #\s
(find #\x "Some sequence") => NIL
(find '(1 2) #(9 3 (1 2) 6 7 8)) => NIL
(find '(1 2) #(9 3 (1 2) 6 7 8) :test #'equal) => (1 2)
(find 1 #(0 1 0 0 0 1 0) :from-end t) => 1
Function indexFull documentation for find (HyperSpec)