e <code>partition</code> is a multiple-valued procedure that takes two
arguments, a predicate and a list, and returns two lists, one comprising
the list elements that satisfy the predicate, the other those that do not.
The purpose of the expression shown is to partition the list
<code>others</code>, sort each of the sublists, and recombine the results
into a sorted list.
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<p>
For our purposes, the important step is the binding of the identifiers
<code>fore</code> and <code>aft</code> to the values retu