132 lines
4.1 KiB
Clojure
132 lines
4.1 KiB
Clojure
(ns vending.core)
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(defn make-default-machine [] { :stock {:apples 5 :oranges 5 :lemons 5}
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:coins {:dollars 1 :quarters 4 :dimes 4 :nickels 4}
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:tendered nil
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:last-message ""
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:change nil
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:output nil} )
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(def coin-values {:dollar 1 :quarter 0.25 :dime 0.10 :nickel 0.05})
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(keys coin-values)
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(.indexOf (keys coin-values) :nickel)
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(def item-prices {:apples 0.65 :oranges 1 :lemons 1.5})
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(defn coin-value [coin]
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(coin-values coin))
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(defn coins-value [coins]
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"Sum the value of these coins."
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(apply + (map coin-value coins)))
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(defn coin-return [machine]
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"Return all tendered coins in this machine."
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(assoc (dissoc machine :tendered) :change (:tendered machine)))
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(defn add-coin [machine coin]
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"Add this coin to this machine."
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(assoc (dissoc machine :tendered) :tendered (cons coin (:tendered machine))))
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(defn add-coins [machine coins]
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"Add these coins to this machine"
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(cond (empty? coins) machine
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true (add-coins (add-coin machine (first coins)) (rest coins))))
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(defn magic-inc [maybenum]
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"A wrapper round inc which treats nil as zero."
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(cond (nil? maybenum) 1
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true (inc maybenum)))
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(defn sum-coin [coin sums]
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"Adds this coin (assumed to be on of :dollars, :quarters, :dimes, :nickels)
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to this map of sums."
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(update-in sums [coin] magic-inc))
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(defn sum-coins
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"takes a list in the form (:dollars :dollars :dimes :quarters :nickels) and returns
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a map {:dollars 2 :quarters 1 :dimes 1 :nickels 1}. Optional second argument: an
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existing map in that general form."
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([coins]
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(sum-coins coins {}))
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([coins sums]
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(cond (empty? coins) sums
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true (sum-coins (rest coins) (sum-coin (first coins) sums)))))
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(defn subtract-denomination [list position]
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(cond (= (count list) position)(cons (- (first list) 1) (rest list))
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true (cons (first list) (subtract-denomination (rest list) position))))
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(defn subtract-nickle [list]
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(subtract-denomination list 1))
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(defn subtract-dime [list]
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(subtract-denomination list 2))
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(defn subtract-quarter [list]
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(subtract-denomination list 3))
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(defn subtract-dollar [list]
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(subtract-denomination list 4))
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(defn in-make-change [amount dollars quarters dimes nickels]
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"Return a tuple (dollars quarters nickels dimes) which indicates the number remaining
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after making change, or nil if not possible"
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(cond
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(= amount 0) (list dollars quarters dimes nickels)
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(and (>= amount (:dollar coin-values)) (> dollars 0))
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(in-make-change (- amount (:dollar coin-values)) (- dollars 1) quarters dimes nickels)
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(and (>= amount (:quarter coin-values)) (> quarters 0))
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(in-make-change (- amount (:quarter coin-values)) dollars (- quarters 1) dimes nickels)
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(and (>= amount (:dime coin-values)) (> dimes 0))
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(in-make-change (- amount (:dime coin-values)) dollars quarters (- dimes 1) nickels)
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(and (>= amount (:nickel coin-values)) (> nickels 0))
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(in-make-change (- amount (:nickel coin-values)) dollars quarters dimes (- nickels 1))))
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(defn make-change [amount dollars quarters dimes nickels]
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(map #(- %1 %2) (list dollars quarters dimes nickels)
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(in-make-change amount dollars quarters dimes nickels)
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))
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(defn subtract-change [machine change]
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"subtract this change from this machine")
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(defn make-change-machine [machine item-price change]
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(let [
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tend (sum-coins (:tendered machine))
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change (make-change item-price (:dollar tend) (:quarter tend) (:dime tend) (:nickel tend))]
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(cond (nil? change) machine)
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true (assoc (dissoc (subtract-change machine change) :change ) :change change )))
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(defn remove-from-stock [machine item]
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machine)
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(defn deliver-item [machine item change]
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(make-change-machine
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(remove-from-stock
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(assoc (dissoc machine :output) :output (cons item (:output machine)))
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item)
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(item item-prices)
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change))
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(defn get-item [machine item]
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(let [item-price (item item-prices)
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tend (sum-coins (:tendered machine))
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change (make-change item-price (:dollar tend) (:quarter tend) (:dime tend) (:nickel tend))]
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(cond (<= 0 (item (:stock machine))) (coin-return machine)
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(<= (coins-value (:tendered machine)) item-price) (coin-return machine)
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(empty? change) (coin-return)
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true (deliver-item machine item change))))
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(defn get-apple [machine]
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(get-item machine :apples))
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