title: Why does using defpackage result in a NAME-CONFLICT?
body: <p>So I'm practicing lisp with Project Euler, and I'm collecting little utility functions into a separate file to reduce duplication, and I expect that it might get pretty huge, so I've gone ahead and made a package definition.  Here is a condensed version of the file that still illustrates my problem:</p>
  
  <pre><code>(defpackage :euler-util
      (:use :common-lisp)
      (:export :divisible-by))
  
  (in-package :euler-util)
  
  (defun divisible-by (x y)
      (equal 0 (mod x y)))
  </code></pre>
  
  <p>I can compile and load (C-c C-k) that file into SLIME without any warnings or errors.  Now, when I go to use it in another file, I do the following:</p>
  
  <pre><code>(load "util.lisp")
  (use-package :euler-util)
  
  (defun euler-1 ()
      (loop for i from 3 to 999 when (or (divisible-by i 3) (divisible-by i 5)) sum i))
  </code></pre>
  
  <p>When I try to compile and load THAT file, I get an error like this:</p>
  
  <p>"USE-PACKAGE # causes name-conflicts in # between the following symbols:  EULER-UTILS:DIVISIBLE-BY, COMMON-LISP-USER::DIVISIBLE-BY [Condition of type NAME-CONFLICT]"</p>
  
  <p>Why is this symbol appearing in the COMMON-LISP-USER package, and how do I stop it?</p>