(iter (for x in '(1 -3 2))
(finding x maximizing (abs x))) => -3

Gauche Scheme

(use gauche.collection :only (find-max))
(find-max '(1 -3 2) :key abs)

-3

Portable Standard Lisp:

(load useful)

(for (in x '(1 -3 2))
(maximal x (abs x)))

-3

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