RE: Predicate for true lists

[Drew Adams <drew.adams@oracle.com>]

> > As for `cdr` vs CDR.  The all-caps version is a metavariable referring
> > to something which we happened to call CDR.  E.g.
> >
> >     Foo takes the form (CAR . CDR) where CDR is blabla.
> 
> Right, but I see no such destructuring/metasyntax in the Elisp manual.
> Both "(elisp) Cons Cells" and "(elisp) Cons Cell Type", for example,
> refer directly to the CAR and CDR slots of a cons cell, without first
> illustrating their structure.  Is that OK?

My answer probably does not reflect an Emacs doc-string or
manual convention, but here are my 2 cents anyway:

1. Uppercase: As Stefan said, only when it refers to a
piece of a pattern.

2. Lowercase in code font (e.g. what Stefan wrote as `cdr`
and you wrote as `cdr'): Only when referring to the function.

3. Lowercase otherwise.  In talking about Lisp, "car" and
"cdr" are regular English words, just like "first" and "rest".
They are Lisp jargon words, but they are English nevertheless.

IOW, there's no reason we should not just talk about the cdr
of a list, with no special typography used for the word "cdr".