When is it not possible to quote nil?

Question

I've never quoted nil before, as I can't see any sense in doing that, but I just played around with some code and it seems that in most cases it is possible to quote nil without any effect. However when I use condition-case with a quoted nil as the first argument, I get an error (wrong-type-argument symbolp (quote nil)).

(condition-case 'nil
    (/ 2 0)
  (error "foo"))

Why does quoting nil cause problems when using it this way ?

Hint: `nil` is not really relevant, e.g., `(condition-case 'some-other-symbol ...)` also doesn't work. — npostavs, Nov 21 '16 at 20:46

sds · Accepted Answer · 2016-11-21T21:39:27.937

2

Whenever the variable in question is evaluated, 'nil and nil are the same.

E.g., all functions (but not necessarily macros and special forms!) get their arguments evaluated.

If it is not evaluated, like the first argument of the special form condition-case, you cannot quote it because then you are passing a list (quote nil) instead of the symbol nil.

edited Nov 21 '16 at 21:39

answered Nov 21 '16 at 20:49

sds

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Thanks for the answer, but I had to read a more detailed answer to understand this http://emacs.stackexchange.com/a/722/11377. – bertfred Nov 21 '16 at 21:14
@bertfred: yes, your question was marked a dupe for a reason! :-) – sds Nov 21 '16 at 21:21
Without your answer I wouldn't have realized, that the macro was the reason ;) – bertfred Nov 21 '16 at 21:26
Technically `condition-case` is not a macro, but a special-form. – politza Nov 21 '16 at 21:36

When is it not possible to quote nil?

1 Answers1