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bug#33998: 27.0.50; cl-delete does not delete the first list element
From: |
João Távora |
Subject: |
bug#33998: 27.0.50; cl-delete does not delete the first list element |
Date: |
Tue, 08 Jan 2019 21:38:17 +0000 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
Drew Adams <drew.adams@oracle.com> writes:
> It's not about implementation of `cl-delete'. It's
> not about the type of sequence you pass it. It's
> about a variable being something different from its
> value.
Drew, it is you who are missing something basic here:
(defun mistery (thing seq)
(let ((head (elt seq 0)))
(cl-delete thing seq)
(eq head (elt seq 0))))
Today, in Emacs this always returns t, for every THING and sequence SEQ
you can think of (in fact, for vectors, cl-delete delegates to cl-remove).
This is perfectly CL-compliant. But a future, different, also perfectly
CL-compliant, implementation of cl-delete, might very well make this
function return nil. In fact, if you port this code to SBCL or Allegro
CL by changing 'cl-delete' to 'cl:delete'
(mistery 1 (list 1 2 3 4)) ;; => t
(mistery 1 (vector 1 2 3 4)) ;; => nil
So again, for the nth time, it's a bad idea to rely on SEQ after calling
'cl-delete'.
João
- bug#33998: 27.0.50; cl-delete does not delete the first list element, (continued)
- bug#33998: 27.0.50; cl-delete does not delete the first list element, João Távora, 2019/01/07
- bug#33998: 27.0.50; cl-delete does not delete the first list element, Drew Adams, 2019/01/07
- bug#33998: 27.0.50; cl-delete does not delete the first list element, João Távora, 2019/01/07
- bug#33998: 27.0.50; cl-delete does not delete the first list element, Drew Adams, 2019/01/07
- bug#33998: 27.0.50; cl-delete does not delete the first list element, João Távora, 2019/01/08
- bug#33998: 27.0.50; cl-delete does not delete the first list element, Drew Adams, 2019/01/08
- bug#33998: 27.0.50; cl-delete does not delete the first list element, João Távora, 2019/01/08
- bug#33998: 27.0.50; cl-delete does not delete the first list element, Drew Adams, 2019/01/08
- bug#33998: 27.0.50; cl-delete does not delete the first list element, João Távora, 2019/01/08
- bug#33998: 27.0.50; cl-delete does not delete the first list element, Drew Adams, 2019/01/08
- bug#33998: 27.0.50; cl-delete does not delete the first list element,
João Távora <=
- bug#33998: 27.0.50; cl-delete does not delete the first list element, Drew Adams, 2019/01/08
bug#33998: 27.0.50; cl-delete does not delete the first list element, Deus Max, 2019/01/07