feb4.rkt

#lang racket

(define x (hash 'n0 1/2
                'n1 1/4
                'n2 1/4))

;; input is some hash, h
(define (max-key h)
  (define keys (hash-keys h))
  (define values (hash-values h))
  (define max-value (apply max values))
  (define key-value-pairs (hash->list h))
  (pretty-print key-value-pairs)
  ;; kvs is a list of key/value pairs
  (define (return-max-key kvs max-val)
    (match kvs
      ['() (error 'impossible)]
      [`(,hd . ,tl) #:when (equal? max-val (cdr hd))
                    (car hd)]
      [`(,hd . ,tl)
       (return-max-key tl max-val)]))
  (return-max-key key-value-pairs max-value))


;; 
(define (last-element l)
  (match l
    [`()           (error 'empty-list)]
    [`(,hd)        hd]
    [`(,hd . ,tl)  (last-element tl)]))

(define (reverse l)
  (match l
    [`()           '()]
    [`(,hd)        `(,hd)]
    [`(,hd . ,tl)  (append (reverse tl) `(,hd))]))


;; going to set each of the keys in h-acc to 1
(define (set-1 keys h-acc)
  (match keys
    [`() h-acc]
    [`(,hd . ,tl) (set-1 tl (hash-set h-acc hd 1))]))