((eq? (car lst) before)
(insert-co new before after (cdr lst) (lambda (new-lst lefts rights) (k (cons new (cons before new-lst)) (succ lefts) rights))))
((eq? (car lst) after)
- (insert-co new before after (cdr lst) (lambda (new-lst lefts rights) (k (cons (after (cons new new-lst))) lefts (succ rights)))))
+ (insert-co new before after (cdr lst) (lambda (new-lst lefts rights) (k (cons after (cons new new-lst)) lefts (succ rights)))))
(else
(insert-co new before after (cdr lst) (lambda (new-lst lefts rights) (k (cons (car lst) new-lst) lefts rights)))))))
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