[racket] Looking for feedback on code style

From: David Van Horn (dvanhorn at ccs.neu.edu)
Date: Thu Sep 9 22:46:49 EDT 2010

On 9/9/10 11:26 AM, Eli Barzilay wrote:
> On Sep  9, David Van Horn wrote:
>> [...] As for the structure of the code as given, I would use helper
>> functions in place of the `let'.  The resulting code will be easier
>> to read and the helper functions can be tested independently, making
>> it easier to maintain and improve the likelihood that the whole
>> program is correct; and correctness and ease of maintenance are
>> important aspects of style.
> Sounds like an overkill in this case, and for most values of
> "idiomatic" I'd say that it'd make it less so.

This is what I had in mind.  I find this solution easier to read and 
reason about.  Is it really overkill?  Less idiomatic?

#lang racket
(require test-engine/racket-tests)

;; A sample is represented as a non-empty list of real numbers.
;; Sample = [Pair Real [Listof Real]]

(check-expect (median (list 1)) 1)
(check-expect (median (list 1 2)) 3/2)
(check-expect (median (list 1 2 3)) 2)
(check-expect (median (list 3 1 2)) 2)
(check-expect (median (list 3 3 2)) 3)

;; Sample -> Real
(define (median lon)
   (median-sorted (sort lon <)
                  (length lon)))

;; Sample Natural -> Real
;; lon is sorted, (= n (length lon)).
(define (median-sorted lon n)
   (cond [(odd? n) (list-ref lon (quotient n 2))]
          (mean (list-ref lon (sub1 (quotient n 2)))
                (list-ref lon (quotient n 2)))]))

;; Real Real -> Real
(define (mean r1 r2)
   (/ (+ r1 r2) 2))


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