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Damn! I had this working (well, with an out-by-one bug), but I decided

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I didn't like how I was representing change. Now the representation of
change is better, but it's breaking again.
This commit is contained in:
simon 2014-03-27 19:40:49 +00:00
parent 0e0c226eea
commit c4fc2fcdd0
1 changed files with 39 additions and 17 deletions
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56
src/vending/core.clj
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@ -21,8 +21,9 @@
(coin-values coin))
(defn coins-value [coins]
"Sum the value of these coins."
(apply + (map coin-value coins)))
"Sum the value of this list of coins."
(cond coins (apply + (map coin-value coins))
true 0))
(defn message-machine [machine message]
@ -97,21 +98,43 @@
(and (>= amount (:bodle coin-values)) (> bodle 0))
(in-make-change (- amount (:bodle coin-values)) merk plack bawbee (- bodle 1))))
(defn make-change [amount merk plack bawbee bodle]
(defn n-of [elt n]
"return a list of n instances of elt"
(cond (<= n 0) nil
true (cons elt (n-of elt (dec n)))))
(defn to-coins [quadtuple]
"Given a list in the form (merks placks bawbies bodles), return a
flat list of coin symbols"
(remove nil?
(flatten
(list
(n-of :merk (nth quadtuple 0))
(n-of :plack (nth quadtuple 1))
(n-of :bawbee (nth quadtuple 2))
(n-of :bodle (nth quadtuple 3))
))))
(defn make-change [amount coins]
"Given this amount of change to make, and this number each of merks, placks, bawbees
and bodles, return a tuple (merk plack bodle bawbee) which indicates the number remaining
after making change, or nil if not possible"
(map #(- %1 %2) (map #(or % 0) (list merk plack bawbee bodle))
(apply in-make-change (map #(or % 0) (list amount merk plack bawbee bodle)))
))
and bodles, return a map with keys (:merk :plack :bawbee :bodle) which indicates the
number of each remaining after making change, or nil if not possible"
(to-coins
(let [merk (:merk coins)
plack (:plack coins)
bawbee (:bawbee coins)
bodle (:bodle coins)]
(map #(- %1 %2) (map #(or % 0) (list merk plack bawbee bodle))
(apply in-make-change (map #(or % 0) (list amount merk plack bawbee bodle)))
))))
(defn subtract-change [coin-stacks change]
"Return a copy of these coin-stacks with this change removed"
{:merk (- (:merk coin-stacks) (nth change 0))
:plack (- (:plack coin-stacks) (nth change 1))
:bawbee (- (:bawbee coin-stacks) (nth change 2))
:bodle (- (:bodle coin-stacks) (nth change 3))})
{:merk (- (:merk coin-stacks) (:merk change))
:plack (- (:plack coin-stacks) (:plack change))
:bawbee (- (:bawbee coin-stacks) (:bawbee change))
:bodle (- (:bodle coin-stacks) (:bodle change))})
(defn subtract-change-machine [machine change]
"return a copy of this machine which has this amount of change removed from its coins"
@ -127,14 +150,13 @@
(defn remove-from-stock [machine item]
"return a copy of this machine with one fewer of this item in stock"
(update-in machine [:items item] dec))
(update-in machine [:stock item] dec))
(defn deliver-item [machine item change]
(make-change-machine
(remove-from-stock
(assoc (dissoc machine :output) :output (cons item (:output machine)))
item)
(item item-prices)
change))
@ -142,9 +164,9 @@
(let [item-price (item item-prices)
coins (:coins machine)
tendered (coins-value (:tendered machine))
change (make-change (- tendered item-price) (:merk coins) (:plack coins) (:bawbee coins) (:bodle coins))]
(print change)
(cond (>= 0 (item (:stock machine))) (message-machine (coin-return machine) (str "Sorry, " item " not in stock"))
change (make-change (- tendered item-price) coins)]
(print (list "hello" item-price coins tendered change ))
(cond (> 0 (item (:stock machine))) (message-machine (coin-return machine) (str "Sorry, " item " not in stock"))
(<= tendered item-price) (message-machine machine "Please insert more money")
(= change '(0 0 0 0)) (message-machine (coin-return machine) "Sorry, I don't have enough change.")
true (message-machine (deliver-item machine item change) (str "Enjoy your " item)))))