[ clisp-Bugs-1383971 ] delete does not remove 1st element in list

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Bugs item #1383971, was opened at 2005-12-17 22:48
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Silvain Dupertuis (silvdup)
Assigned to: Nobody/Anonymous (nobody)
Summary: delete does not remove 1st element in list

Initial Comment:
The macro DELETE does not remove the first element of a
list
- It does remove correctly other elements, but not the
first.
- It does remove the first element on a vector, not on
a list.
- The element is correctly removed in the resulting
form, but not in the original list when it is the first
element of the list.
<I>Example</I>
;;; Test for macro delete
(let ((x '(12 13 14 15 12 13)))  
  (loop
    for i from 0 below (length x)
    do
    (let* ((y (copy-seq x))
           (z (nth i x))
           (y- (delete z y)))
      (format t 
          "~%~A~%~A : x =        ~A
    y (copy) = ~A
    element    ~A
    result   = ~A
    y      >>= ~A~%"
        "------------------------------------------"
        i x y z y- y)))
  (format t "~A~%~A~%~A~%~A~%"
    "----------------------------------------------------"
    "result shoud be each time the same as last y"
    "it does not work for the first element of the liste"
   
"===================================================="))
;;; End of test
The bug seems to be deep in the language itself. I have
tested it with
- Allegro CL 7.0 Trial
- LispWorks 4.4
- Maxima (but in Maxima Lisp, delete does not work
destructively on vectors at all)
-------------------
It took me some time to discover where the bug was in a
program I was working on... then I made an alternate
delete0 macro to work around
-------------------


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