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primarykey
Id
12333692
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2012-09-08T19:14:36.497
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2012-09-08T22:08:51.260
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2012-09-08T22:08:51.260
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12333590
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2
Score
4
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text
Body
Actually, <code>x</code> is local to the function, so <code>setf</code> or <code>setq</code>ing it only changes the local variable <code>x</code>. To answer the second part of your question, there is another way to define a local variable other than let: <pre><code>(funcall (lambda (var1 var2...) ... use var1 var2 ...)- val1 val2 ...) </code></pre> In fact, <code>defun</code> could be implemented as <pre><code>`(setf (symbol-function ,name) (lambda ,args ,@body)) </code></pre> though all the implementations I've checked do more than that. Also, the <code>symbol-function</code> place allows you to do this: <pre><code>(setf (symbol-function '+) (function -)) </code></pre> though that's generally a bad idea. <h2>Your second question</h2> What's happening there is that <code>x</code> is local to the scope that contains the <code>defun</code>. It's not a global variable. What you're doing with that <code>defun</code> is creating a closure that "captures" all the lexically-scoped (not created with <code>defvar</code>/<code>defparameter</code>) variables in the surrounding scopes and holds on to them for the future. If you want to inspect the value of <code>x</code>, add another function <pre><code>(defun get-x () x) </code></pre> inside the <code>let</code>. To put it another way, <code>x</code> is local to the <code>let</code> that the function is in. The situation you've provided is similar to: <pre><code>(let ((x 3)) (print x) (let ((y 7)) (print (list x y)) (setf x y)) (print x)) </code></pre> except the inner <code>let</code> is replaced by a <code>defun</code> (which is a <code>lambda</code>).
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1. POLISP local/global variable assignment
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