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  1. PO
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    <p>Your function is always returning <code>'()</code>, I think (can't be sure since you didn't show the whole thing).</p> <p>Perhaps:</p> <pre><code>(defun delete-bindings! (var symbol-table) (cond ((endp symbol-table) '()) ((eql var (caar symbol-table)) (delete-bindings! var (cdr symbol-table))) (t (progn (setf (cdr symbol-table) (delete-bindings! var (cdr symbol-table))) symbol-table))) </code></pre> <p>Addendum:</p> <p>You must use the result of this function, not simply depend on its side effects:</p> <pre><code>(setq *bindings* (delete-bindings! 'var *bindings*)) </code></pre> <p>Second addendum</p> <pre><code>Loading ~/ccl-init.lisp Welcome to Clozure Common Lisp Version 1.7-dev-r14406M-trunk (DarwinX8632)! ? (defun delete-bindings! (var symbol-table) (cond ((endp symbol-table) '()) ((eql var (caar symbol-table)) (delete-bindings! var (cdr symbol-table))) (t (progn (setf (cdr symbol-table) (delete-bindings! var (cdr symbol-table))) symbol-table)))) DELETE-BINDINGS! ? (delete-bindings! 'a '((a . 3) (b . 2))) ((B . 2)) ? </code></pre> <p>If you need a data structure that may be destructively modified with all references to it updated, you'll need another level of indirection.</p> <p>E.g.,</p> <pre><code>(defvar *symbol-table* (cons 'bindings '((a . 3) (b . 2)))) (defun delete-bindings! (var symbol-table) (flet ((db! (var symbol-table) (cond ((endp symbol-table) '()) ((eql var (caar symbol-table)) (delete-bindings! var (cdr symbol-table))) (t (progn (setf (cdr symbol-table) (delete-bindings! var (cdr symbol-table))) symbol-table))))) (rplacd symbol-table (db! var (cdr symbol-table))))) </code></pre>
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    1. POCommon Lisp, remove element from list destructive
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    1. USDoug Currie
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    1. POCommon Lisp, remove element from list destructive
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    1. COYes I missed the last line of code when posting, now its complete. Thanks, but it does not work.
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    2. COSee my addendum; the function doesn't change the places that refer to the old value of the list (it can't since you pass the list of bindings by value, not by reference).
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    3. COIf I understood right what you mean then delete-bindings shouldn't work for symbol-table: '((a . 2) (b . 3)) and var: 'b. But it's possible to delete 'b but not 'a with my function.
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