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    <p><code>/</code> takes as arguments one or more numbers, but in your code you're passing it a list - clearly this will not work. The function <code>apply</code> is your friend here - <code>(apply #'foo a b (list c d e))</code> is equivalent to <code>(foo a b c d e)</code>. Note the the arguments to <code>apply</code> between the function to use and the final list are optional, so <code>(apply #'/ '(20 2 5))</code> is equivalent to <code>(/ 20 2 5)</code>.</p> <p>Also, your attempt at removing zeros will not work. <code>dolist</code> is evaluating its body for each item in the argument list <code>elements</code>, but you're not actually doing anything to change the content of <code>elements</code> (the result of evaluating <code>dolist</code> s body is not reassigned to the source element as you seem to expect).</p> <p>The functions <code>remove-if</code> (and its destructive counterpart, <code>delete-if</code>) are what you are looking for. The following shows how to use it (it takes lots of optional arguments, which you don't need to worry about for this purpose).</p> <pre><code>(defun divtest (elements) (apply #'/ (remove-if #'zerop elements))) </code></pre> <p>Also note that this won't behave correctly if the <code>elements</code> list has zero as its first element (assuming I understand what the function's meant to do). So you might instead want something like</p> <pre><code>(defun divtest (elements) (apply #'/ (first elements) (remove-if #'zerop (rest elements)))) </code></pre> <p>See the Hyperspec for more details.</p>
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    1. POdefun with a list as argument
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    1. POdefun with a list as argument
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    1. COuse REDUCE instead of APPLY
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    2. COJust curious: what would the utility of that be?
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    3. COthis way you could process arbitrary long lists and not only those of CALL-ARGUMENT-LIMIT (a standard CL constant) max length. Common Lisp has a an implementation dependent max number of arguments. This number has to be 50 or larger. This means that an implementation does only need to support 50 arguments (or more). Thus your above function might fail in some implementation where the list of numbers is longer than the number of arguments calling the function / allows.
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