A sequence is an ordered collection of elements, implemented as either a vector or a list.
Sequences can be created by the function make-sequence, as well as other functions that create objects of types that are subtypes of sequence (e.g., list, make-list, mapcar, and vector).
A sequence function is a function defined by this specification or added as an extension by the implementation that operates on one or more sequences. Whenever a sequence function must construct and return a new vector, it always returns a simple vector. Similarly, any strings constructed will be simple strings.
Figure 17-1. Standardized Sequence Functions
concatenate length remove
copy-seq map remove-duplicates
count map-into remove-if
count-if merge remove-if-not
count-if-not mismatch replace
delete notany reverse
delete-duplicates notevery search
delete-if nreverse some
delete-if-not nsubstitute sort
elt nsubstitute-if stable-sort
every nsubstitute-if-not subseq
fill position substitute
find position-if substitute-if
find-if position-if-not substitute-if-not
find-if-not reduce
17.1.1 General Restrictions on Parameters that must be Sequences