[plt-scheme] simple scheme idiom for generalized maximum?

(define (longest-string los)
   (first (sort los > #:key string-length)))


On Sep 23, 2009, at 2:08 PM, John Clements wrote:

> I'm sure this has been beaten to death somewhere, but I can't think  
> of a natural way to find, e.g., the longest string in a list. It's  
> easy to define maximumBy in terms of foldl1 (which I claim should be  
> in there already), but seems like there should be an obvious way to  
> do this using library functions.
>
> Am I missing something obvious?
>
> John
>
>
> (define (foldl1 f l)
>  (foldl f (first l) (rest l)))
>
> (define (maximumBy f lst)
>  (foldl1 (lambda (a b) (if (f a b) a b)) lst))
>
> (maximumBy (lambda (a b) (> (string-length a) (string-length b)))
>           `("abc" "abcd" "ab"))
>
>
> => "abcd"
>
>
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