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Refer to "proper lists" instead of "true lists"

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* doc/lispref/lists.texi (Cons Cells, Building Lists):
* doc/lispref/sequences.texi (Vector Functions): Use the more
popular term "proper", rather than "true", to qualify nil-terminated
lists.

For discussion, see the following emacs-devel subthreads:
https://lists.gnu.org/archive/html/emacs-devel/2018-06/msg00112.html
https://lists.gnu.org/archive/html/emacs-devel/2018-06/msg00138.html
This commit is contained in:
Basil L. Contovounesios 2018-07-10 19:51:28 -07:00 • committed by Paul Eggert
parent 35e0305dc2
commit db3874b161
2 changed files with 13 additions and 10 deletions
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21
doc/lispref/lists.texi
View file

@ -50,16 +50,19 @@ convention; at the level of cons cells, the @sc{car} and @sc{cdr}
slots have similar properties). Hence, the @sc{cdr} slot of each cons slots have similar properties). Hence, the @sc{cdr} slot of each cons
cell in a list refers to the following cons cell. cell in a list refers to the following cons cell.
@cindex proper list
@cindex true list @cindex true list
Also by convention, the @sc{cdr} of the last cons cell in a list is Also by convention, the @sc{cdr} of the last cons cell in a list is
@code{nil}. We call such a @code{nil}-terminated structure a @code{nil}. We call such a @code{nil}-terminated structure a
@dfn{true list}. In Emacs Lisp, the symbol @code{nil} is both a @dfn{proper list}@footnote{It is sometimes also referred to as a
symbol and a list with no elements. For convenience, the symbol @dfn{true list}, but we generally do not use this terminology in this
@code{nil} is considered to have @code{nil} as its @sc{cdr} (and also manual.}. In Emacs Lisp, the symbol @code{nil} is both a symbol and a
as its @sc{car}). list with no elements. For convenience, the symbol @code{nil} is
considered to have @code{nil} as its @sc{cdr} (and also as its
@sc{car}).
Hence, the @sc{cdr} of a true list is always a true list. The Hence, the @sc{cdr} of a proper list is always a proper list. The
@sc{cdr} of a nonempty true list is a true list containing all the @sc{cdr} of a nonempty proper list is a proper list containing all the
elements except the first. elements except the first.
@cindex dotted list @cindex dotted list
@ -71,10 +74,10 @@ Pair Notation}). There is one other possibility: some cons cell's
@sc{cdr} could point to one of the previous cons cells in the list. @sc{cdr} could point to one of the previous cons cells in the list.
We call that structure a @dfn{circular list}. We call that structure a @dfn{circular list}.
For some purposes, it does not matter whether a list is true, For some purposes, it does not matter whether a list is proper,
circular or dotted. If a program doesn't look far enough down the circular or dotted. If a program doesn't look far enough down the
list to see the @sc{cdr} of the final cons cell, it won't care. list to see the @sc{cdr} of the final cons cell, it won't care.
However, some functions that operate on lists demand true lists and However, some functions that operate on lists demand proper lists and
signal errors if given a dotted list. Most functions that try to find signal errors if given a dotted list. Most functions that try to find
the end of a list enter infinite loops if given a circular list. the end of a list enter infinite loops if given a circular list.
@ -522,7 +525,7 @@ object. The final argument is not copied or converted; it becomes the
is itself a list, then its elements become in effect elements of the is itself a list, then its elements become in effect elements of the
result list. If the final element is not a list, the result is a result list. If the final element is not a list, the result is a
dotted list since its final @sc{cdr} is not @code{nil} as required dotted list since its final @sc{cdr} is not @code{nil} as required
in a true list. in a proper list (@pxref{Cons Cells}).
@end defun @end defun
Here is an example of using @code{append}: Here is an example of using @code{append}:

2
doc/lispref/sequences.texi
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@ -1355,7 +1355,7 @@ each initialized to @var{object}.
@defun vconcat &rest sequences @defun vconcat &rest sequences
@cindex copying vectors @cindex copying vectors
This function returns a new vector containing all the elements of This function returns a new vector containing all the elements of
@var{sequences}. The arguments @var{sequences} may be true lists, @var{sequences}. The arguments @var{sequences} may be proper lists,
vectors, strings or bool-vectors. If no @var{sequences} are given, vectors, strings or bool-vectors. If no @var{sequences} are given,
the empty vector is returned. the empty vector is returned.