Betting.rkt

betting.rkt

#lang racket/base

;; utilities
(struct Bet (name target monies) #:transparent)

(define *bets*   (make-parameter '()))
(define *total*  (make-parameter 0.0))
(define *wagers* (make-parameter (make-immutable-hash)))

(define (sum datums) (foldl + 0.0 datums))

(define (produce-wager-table bets)
  (define total (sum (map Bet-monies bets)))
  (define (reducer b hashy)
    (let ([key (Bet-target b)]
          [val (Bet-monies b)])
      (if (hash-has-key? hashy key)
          (hash-update hashy key (λ (x) (+ x val)))
          (hash-set hashy key val))))
  (foldl reducer (make-immutable-hash) bets))

;; user interface

(define (clear-bets)
  (*total* 0.0)
  (*wagers* (make-immutable-hash))
  (*bets* '()))

(define (place-bet Name Target Monies)
  (*total* (+ (*total*) Monies))
  (*bets* (cons (Bet Name Target Monies) (*bets*)))
  (*wagers* (produce-wager-table (*bets*))))

(define (bets)
  (for-each displayln (*bets*))
  (displayln (format "Pool: $~a" (*total*))))

(define (odds)
  (for-each
   (λ (key)
     (displayln
      (format "~a -> ~a" key
              (/ (*total*) (hash-ref (*wagers*) key)))))
   (hash-keys (*wagers*)))
  (displayln (format "Total: ~a" (*total*))))


; end