[<A HREF="Permutation.ps">PostScript</A>]

<PRE>
Permutation (E, C): <b>trait</b>
  % Test for having the same elements
  <b>assumes</b> <A HREF="Container.html">Container</A>
  <b>includes</b>
    <A HREF="Bag.html">Bag</A> (B <b>for</b> C),
    <A HREF="CoerceContainer.html">CoerceContainer</A> (C <b>for</b> DC, B <b>for</b> RC) 
  <b>introduces</b> isPermutation: C, C -&gt; Bool
  <b>asserts</b> <b>forall</b> c1, c2: C
      isPermutation(c1, c2) == coerce(c1) = coerce(c2)
  <b>implies</b> <b>forall</b> e: E, c1, c2: C
    isPermutation(c1, c2)
      =&gt; count(e, c1) = count(e, c2)</PRE>

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