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Improve documentation of 'copy-sequence'

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* src/fns.c (Fcopy_sequence):
* doc/lispref/sequences.texi (Sequence Functions): Mention the
exception when copying an empty sequence.  (Bug#28627)
This commit is contained in:
Eli Zaretskii 2017-09-30 16:01:00 +03:00
parent 200ef6f721
commit cb93a6ce72
2 changed files with 7 additions and 2 deletions
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5
doc/lispref/sequences.texi
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@ -155,7 +155,10 @@ This function generalizes @code{aref} (@pxref{Array Functions}) and
@cindex copying sequences @cindex copying sequences
This function returns a copy of @var{seqr}, which should be either a This function returns a copy of @var{seqr}, which should be either a
sequence or a record. The copy is the same type of object as the sequence or a record. The copy is the same type of object as the
original, and it has the same elements in the same order. original, and it has the same elements in the same order. However, if
@var{seqr} is empty, like a string or a vector of zero length, the
value returned by this function might not be a copy, but an empty
object of the same type and identical to @var{seqr}.
Storing a new element into the copy does not affect the original Storing a new element into the copy does not affect the original
@var{seqr}, and vice versa. However, the elements of the copy @var{seqr}, and vice versa. However, the elements of the copy

4
src/fns.c
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@ -482,7 +482,9 @@ usage: (vconcat &rest SEQUENCES) */)
DEFUN ("copy-sequence", Fcopy_sequence, Scopy_sequence, 1, 1, 0, DEFUN ("copy-sequence", Fcopy_sequence, Scopy_sequence, 1, 1, 0,
doc: /* Return a copy of a list, vector, string, char-table or record. doc: /* Return a copy of a list, vector, string, char-table or record.
The elements of a list, vector or record are not copied; they are The elements of a list, vector or record are not copied; they are
shared with the original. */) shared with the original.
If the original sequence is empty, this function may return
the same empty object instead of its copy. */)
(Lisp_Object arg) (Lisp_Object arg)
{ {
if (NILP (arg)) return arg; if (NILP (arg)) return arg;