2014-05-15 Dmitry Antipov <dmantipov@yandex.ru>
* lists.texi (Building Cons Cells and Lists): Remove
- description of `reverse' and generalize it...
+ description of `reverse' and `'nreverse' to generalize them...
* sequences.texi (Sequences): ...for sequences here.
2014-05-14 Glenn Morris <rgm@gnu.org>
@end smallexample
@end defun
-@defun nreverse list
-@cindex reversing a list
- This function reverses the order of the elements of @var{list}.
-Unlike @code{reverse}, @code{nreverse} alters its argument by reversing
-the @sc{cdr}s in the cons cells forming the list. The cons cell that
-used to be the last one in @var{list} becomes the first cons cell of the
-value.
-
- For example:
-
-@example
-@group
-(setq x '(a b c))
- @result{} (a b c)
-@end group
-@group
-x
- @result{} (a b c)
-(nreverse x)
- @result{} (c b a)
-@end group
-@group
-;; @r{The cons cell that was first is now last.}
-x
- @result{} (a)
-@end group
-@end example
-
- To avoid confusion, we usually store the result of @code{nreverse}
-back in the same variable which held the original list:
-
-@example
-(setq x (nreverse x))
-@end example
-
- Here is the @code{nreverse} of our favorite example, @code{(a b c)},
-presented graphically:
-
-@smallexample
-@group
-@r{Original list head:} @r{Reversed list:}
- ------------- ------------- ------------
-| car | cdr | | car | cdr | | car | cdr |
-| a | nil |<-- | b | o |<-- | c | o |
-| | | | | | | | | | | | |
- ------------- | --------- | - | -------- | -
- | | | |
- ------------- ------------
-@end group
-@end smallexample
-@end defun
-
@defun sort list predicate
@cindex stable sort
@cindex sorting lists
@end example
@end defun
+@defun nreverse seq
+@cindex reversing a list
+@cindex reversing a vector
+ This function reverses the order of the elements of @var{seq}.
+If @var{seq} is a list, @code{nreverse} alters its by reversing the @sc{cdr}s
+in the cons cells. The cons cell that used to be the last one in @var{seq}
+becomes the first cons cell of the value. If @var{seq} is a vector or
+bool vector, its items are placed in the same vector in a reversed order.
+
+ For example:
+
+@example
+@group
+(setq x '(a b c))
+ @result{} (a b c)
+@end group
+@group
+x
+ @result{} (a b c)
+(nreverse x)
+ @result{} (c b a)
+@end group
+@group
+;; @r{The cons cell that was first is now last.}
+x
+ @result{} (a)
+@end group
+@end example
+
+ To avoid confusion, we usually store the result of @code{nreverse}
+back in the same variable which held the original list:
+
+@example
+(setq x (nreverse x))
+@end example
+
+ Here is the @code{nreverse} of our favorite example, @code{(a b c)},
+presented graphically:
+
+@smallexample
+@group
+@r{Original list head:} @r{Reversed list:}
+ ------------- ------------- ------------
+| car | cdr | | car | cdr | | car | cdr |
+| a | nil |<-- | b | o |<-- | c | o |
+| | | | | | | | | | | | |
+ ------------- | --------- | - | -------- | -
+ | | | |
+ ------------- ------------
+@end group
+@end smallexample
+
+ For the vector, it is even simpler because you don't need setq:
+
+@example
+(setq x [1 2 3 4])
+ @result{} [1 2 3 4]
+(nreverse x)
+ @result{} [4 3 2 1]
+x
+ @result{} [4 3 2 1]
+@end example
+
+Note that unlike @code{reverse}, this function doesn't work with strings.
+Although you can alter string data by using @code{aset}, it is strongly
+encouraged to treat strings as immutable.
+
+@end defun
+
@node Arrays
@section Arrays
@cindex array
2014-05-15 Dmitry Antipov <dmantipov@yandex.ru>
* fns.c (Freverse): Allow vectors, bool vectors and strings.
+ (Fnreverse): Allow vectors and bool vectors.
2014-05-14 Dmitry Antipov <dmantipov@yandex.ru>
}
DEFUN ("nreverse", Fnreverse, Snreverse, 1, 1, 0,
- doc: /* Reverse LIST by modifying cdr pointers.
-Return the reversed list. Expects a properly nil-terminated list. */)
- (Lisp_Object list)
+ doc: /* Reverse order of items in a list or vector SEQ.
+If SEQ is a list, it should be nil-terminated, and reversed
+by modifying cdr pointers. Return the reversed SEQ.
+
+Note that unlike `reverse', this function doesn't work with strings.
+It is strongly encouraged to treat them as immutable. */)
+ (Lisp_Object seq)
{
- register Lisp_Object prev, tail, next;
+ if (NILP (seq))
+ return seq;
+ else if (CONSP (seq))
+ {
+ Lisp_Object prev, tail, next;
- if (NILP (list)) return list;
- prev = Qnil;
- tail = list;
- while (!NILP (tail))
+ for (prev = Qnil, tail = seq; !NILP (tail); tail = next)
+ {
+ QUIT;
+ CHECK_LIST_CONS (tail, tail);
+ next = XCDR (tail);
+ Fsetcdr (tail, prev);
+ prev = tail;
+ }
+ seq = prev;
+ }
+ else if (VECTORP (seq))
{
- QUIT;
- CHECK_LIST_CONS (tail, tail);
- next = XCDR (tail);
- Fsetcdr (tail, prev);
- prev = tail;
- tail = next;
+ ptrdiff_t i, size = ASIZE (seq);
+
+ for (i = 0; i < size / 2; i++)
+ {
+ Lisp_Object tem = AREF (seq, i);
+ ASET (seq, i, AREF (seq, size - i - 1));
+ ASET (seq, size - i - 1, tem);
+ }
}
- return prev;
+ else if (BOOL_VECTOR_P (seq))
+ {
+ ptrdiff_t i, size = bool_vector_size (seq);
+
+ for (i = 0; i < size / 2; i++)
+ {
+ bool tem = bool_vector_bitref (seq, i);
+ bool_vector_set (seq, i, bool_vector_bitref (seq, size - i - 1));
+ bool_vector_set (seq, size - i - 1, tem);
+ }
+ }
+ else
+ wrong_type_argument (Qarrayp, seq);
+ return seq;
}
DEFUN ("reverse", Freverse, Sreverse, 1, 1, 0,
2014-05-15 Dmitry Antipov <dmantipov@yandex.ru>
* automated/fns-tests.el: New file.
+ * automated/fns-tests.el (fns-tests-nreverse)
+ (fns-tests-nreverse-bool-vector): New tests.
2014-05-08 Glenn Morris <rgm@gnu.org>
(should-error (reverse))
(should-error (reverse 1))
(should-error (reverse (make-char-table 'foo)))
+ (should (equal [] (reverse [])))
+ (should (equal [0] (reverse [0])))
(should (equal [1 2 3 4] (reverse (reverse [1 2 3 4]))))
+ (should (equal '(a b c d) (reverse (reverse '(a b c d)))))
(should (equal "xyzzy" (reverse (reverse "xyzzy"))))
(should (equal "こんにちは / ｺﾝﾆﾁﾊ" (reverse (reverse "こんにちは / ｺﾝﾆﾁﾊ")))))
+(ert-deftest fns-tests-nreverse ()
+ (should-error (nreverse))
+ (should-error (nreverse 1))
+ (should-error (nreverse (make-char-table 'foo)))
+ (should-error (nreverse "xyzzy"))
+ (let ((A []))
+ (nreverse A)
+ (should (equal A [])))
+ (let ((A [0]))
+ (nreverse A)
+ (should (equal A [0])))
+ (let ((A [1 2 3 4]))
+ (nreverse A)
+ (should (equal A [4 3 2 1])))
+ (let ((A [1 2 3 4]))
+ (nreverse A)
+ (nreverse A)
+ (should (equal A [1 2 3 4])))
+ (let* ((A [1 2 3 4])
+ (B (nreverse (nreverse A))))
+ (should (equal A B))))
+
(ert-deftest fns-tests-reverse-bool-vector ()
(let ((A (make-bool-vector 10 nil)))
(dotimes (i 5) (aset A i t))
(should (equal [nil nil nil nil nil t t t t t] (vconcat (reverse A))))
(should (equal A (reverse (reverse A))))))
+
+(ert-deftest fns-tests-nreverse-bool-vector ()
+ (let ((A (make-bool-vector 10 nil)))
+ (dotimes (i 5) (aset A i t))
+ (nreverse A)
+ (should (equal [nil nil nil nil nil t t t t t] (vconcat A)))
+ (should (equal [t t t t t nil nil nil nil nil] (vconcat (nreverse A))))))
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