Here's a quick summary of using SORT. For more details, look in Steele
or do "clman sort".

Basic form: (sort <List> <Predicate>)

<Predicate> is basically a greater-than or less-than function that
operates on entries of the type in <List>. Ie it should be a function of 2
arguments, each of which is of the type contained in <List>, and
return T if they are in order, NIL otherwise.

Examples

> (setq Test '(1 2 3 4 3 2 1))
(1 2 3 4 3 2 1)

> (setq Test (sort Test #'>))
(4 3 3 2 2 1 1)

> (setq Test (sort Test #'<))
(1 1 2 2 3 3 4)

> (setq Test2 '((A 1) (B 2) (C 3) (B 2) (A 1)))
((A 1) (B 2) (C 3) (B 2) (A 1))

> (defun Val (Entry)
    "Return the value part of a (LETTER VALUE) pair"
     (second Entry))
VAL

> (defun Greater-Val? (Entry1 Entry2)
    "Is the Val part of Entry1 bigger than Val part of Entry2?"
    (> (Val Entry1) (Val Entry2)))
GREATER-VAL?

> (setq Test2 (sort Test2 #'Greater-Val?))
((C 3) (B 2) (B 2) (A 1) (A 1))