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.
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