Commit ddc30c99 authored by Dmitry Antipov's avatar Dmitry Antipov

* src/fns.c (Fnreverse): Allow vectors and bool vectors.

* doc/lispref/lists.texi (Building Cons Cells and Lists): Remove
description of `nreverse' and generalize it...
* doc/lispref/sequences.texi (Sequences): ...for sequences here.
* tests/automated/fns-tests.el (fns-tests-nreverse)
(fns-tests-nreverse-bool-vector): New tests.
parent 92491099
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>
......
......@@ -1124,58 +1124,6 @@ each time you run it! Here is what happens:
@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
......
......@@ -260,6 +260,75 @@ x
@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>
......
......@@ -1697,25 +1697,55 @@ changing the value of a sequence `foo'. */)
}
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>
......
......@@ -28,12 +28,44 @@
(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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