A vector is a basic integer-indexed collection, a one-dimensional array. Vectors and lists are collectively considered to be sequences. If the sequence seq contains an element satisfying test, then the leftmost such element is returned, otherwise nil is returned. Functional variants are find-if and find-if-not. The number of elements in the specified subsequence of seq. Functional variants are count-if and count-if-not. Returns first element of sequence if it were ordered by sort using the predicate fn. extrema is similar but returns a list of values since there may be more than one extremum determined by the predicate. n-most-extreme returns a list of n values of a sorted sequence. ref Decreases the fill pointer of vector by one, and retrieves the element of vector that is designated by the new fill pointer. Splits sequence into a list of subsequences delimited by objects satisfying the test. Also returns the lenbth of the sequence idx. Functional variants are cl-utilities:split-sequence-if and cl-utilities:split-sequence-if-not. Destructively replaces the elements of se1 bounded by :start1 and :end1 with the elements of seq2 bounded by :start2 and :end2. Functional variants are substitute-if, substitute-if-not. Destructive variants are nsubstitute, nsubstitute-if, and nsubstitute-if-not. subst performs substitutions throughout a tree. Functional variants are remove-if and remove-if-not. The destructive variants are delete, delete-if, and delete-if-not. To remove in place, use alexandria:removef or alexandria:deletef. Reverse the order of elements in a sequence. The destructive version is nreverse. To save the result in place, use alexandria:reversef. The sequence is destructively sorted according to an order determined by the predicate fn. stable-sort guarantees equal elements stay in same order. Destructively concatenates the two sequences and sorts the combined elements based on the predicate fn. Returns a random permutation of a sequence bounded by :start and :end. The original sequence may be modified. Applies the function to elements of each sequence in turn. The result sequence is as long as the shortest of the sequences. Destructively modifies result-seq to contain the results of applying the function to each element in the argument seqs in turn. Source.