reverse sequence → reversed-sequence

nreverse sequence → reversed-sequence

sequence — a proper sequence.

reversed-sequence — a sequence.

reverse and nreverse return a new sequence of the same kind as sequence, containing the same elements, but in reverse order.

reverse and nreverse differ in that reverse always creates and returns a new sequence, whereas nreverse might modify and return the given sequence. reverse never modifies the given sequence.

For reverse, if sequence is a vector, the result is a fresh simple array of rank one that has the same actual array element type as sequence. If sequence is a list, the result is a fresh list.

For nreverse, if sequence is a vector, the result is a vector that has the same actual array element type as sequence. If sequence is a list, the result is a list.

For nreverse, sequence might be destroyed and re-used to produce the result. The result might or might not be identical to sequence. Specifically, when sequence is a list, nreverse is permitted to setf any part, car or cdr, of any cons that is part of the list structure of sequence. When sequence is a vector, nreverse is permitted to re-order the elements of sequence in order to produce the resulting vector.

(setq str "abc") → "abc" 
(reverse str) → "cba" 
str → "abc" 
(setq str (copy-seq str)) → "abc" 
(nreverse str) → "cba" 
str → implementation-dependent 
(setq l (list 1 2 3)) → (1 2 3) 
(nreverse l) → (3 2 1) 
l → implementation-dependent

nreverse might either create a new sequence, modify the argument sequence, or both. (reverse does not modify sequence.)

Should be prepared to signal an error of type type-error if sequence is not a proper sequence.