listp docstring.

listp docstring.

[Luc Teirlinck]

I do not exactly want to start another thread of the car/cdr type.
But the docstring of listp _really_ can be unclear _even_ for people
who know Lisp.  The current docstring is:

Return t if object is a list.  This includes nil.

But "list" is ambiguous: its strict meaning, intended here, is
"cons cell or nil".  But it is very often used informally in the sense
of "true list", including in some other docstrings.  The car/cdr
thread has shown that there really is some potential confusion here,
since many people do understand list as "true list".

What about the following docstring, which I can install if desired:

Return t if OBJECT is a list, that is, a cons cell or nil.
Otherwise, return nil.

Sincerely,

Luc.

Re: listp docstring.

[Luc Teirlinck]

Maybe I should point out that the references to "list" in the
docstrings of car and cdr are not as ambiguous as the one in listp,
because these docstrings do contain a reference to "cons cell or nil"
in their second line.  This seems (to me) to make the meaning clear.
The present `listp' docstring contains no such reference.

Docstring of car:

     Return the car of list.  If arg is nil, return nil.
     Error if arg is not nil and not a cons cell.  See also `car-safe'.

     See Info node `(elisp)Cons Cells' for a discussion of related basic
     Lisp concepts such as car, cdr, cons cell and list.

Re: listp docstring.

[Richard M. Stallman]

    What about the following docstring, which I can install if desired:

    Return t if OBJECT is a list, that is, a cons cell or nil.
    Otherwise, return nil.

Please install it.