(ns foo)

;;; This is a library for the shopping result.

(defrecord Banana [qty])
(defrecord Grape  [qty])
(defrecord Orange [qty])

;;; 'subtotal' differs from each fruit.

(defprotocol Fruit
  (subtotal [item]))

(extend-type Banana
  Fruit
  (subtotal [item]
    (* 158 (:qty item))))

(extend-type Grape
  Fruit
  (subtotal [item]
    (* 178 (:qty item))))

(extend-type Orange
  Fruit
  (subtotal [item]
    (* 98 (:qty item))))

;;; 'coupon' is the function returing a 'reify' of subtotal. This is
;;; when someone uses a coupon ticket, the price of some fruits is 
;;; taken off 25%.

(defn coupon [item]
  (reify Fruit
    (subtotal [_]
      (int (* 0.75 (subtotal item))))))

;;; Example: To compute the total when someone bought 10 oranges,
;;;  15 bananas and 10 grapes using a coupon.
;;; foo=> (apply +  (map subtotal [(Orange. 10) (Banana. 15) (coupon (Grape. 10))]))
;;; 4685            ; (apply + '(980 2370 1335))
;;; foo=> 

(ns foo)

;;; This is a library for the shopping result.

(defrecord Banana [qty])
(defrecord Grape  [qty])
(defrecord Orange [qty])

;;; 'subtotal' differs from each fruit.

(defprotocol Fruit
  (subtotal [item]))

(extend-type Banana
  Fruit
  (subtotal [item]
    (* 158 (:qty item))))

(extend-type Grape
  Fruit
  (subtotal [item]
    (* 178 (:qty item))))

(extend-type Orange
  Fruit
  (subtotal [item]
    (* 98 (:qty item))))

;;; 'coupon' is the function returing a 'reify' of subtotal. This is
;;; when someone uses a coupon ticket, some fruits price off 25%.

(defn coupon [item]
  (reify Fruit
    (subtotal [_]
      (int (* 0.75 (subtotal item))))))

;;; Example: To compute the total when someone bought 10 oranges,
;;;  15 bananas and 10 grapes using a coupon.
;;; foo=> (apply +  (map subtotal [(Orange. 10) (Banana. 15) (coupon (Grape. 10))]))
;;; 4685            ; (apply + '(980 2370 1335))
;;; foo=> 

(ns foo)

;;; This is a library for the shopping result.

(defrecord Banana [qty])
(defrecord Grape  [qty])
(defrecord Orange [qty])

;;; 'subtotal' differs from each fruit.

(defprotocol Fruit
  (subtotal [item]))

(extend-type Banana
  Fruit
  (subtotal [item]
    (* 158 (:qty item))))

(extend-type Grape
  Fruit
  (subtotal [item]
    (* 178 (:qty item))))

(extend-type Orange
  Fruit
  (subtotal [item]
    (* 98 (:qty item))))

;;; 'coupon' is the function returing a 'reify' of subtotal. This is
;;; when someone uses a coupon ticket, some fruits price down 25%.

(defn coupon [item]
  (reify Fruit
    (subtotal [_]
      (int (* 0.75 (subtotal item))))))

;;; Example: To compute the total when someone bought 10 oranges,
;;;  15 bananas and 10 grapes using a coupon.
;;; foo=> (apply +  (map subtotal [(Orange. 10) (Banana. 15) (coupon (Grape. 10))]))
;;; 4685            ; (apply + '(980 2370 1335))
;;; foo=> 

;;; This is a library for the shopping result.

(defrecord Banana [qty])
(defrecord Grape  [qty])
(defrecord Orange [qty])

;;; 'subtotal' differs from each fruit.

(defprotocol Fruit
  (subtotal [item]))

(extend-type Banana
  Fruit
  (subtotal [item]
    (* 158 (:qty item))))

(extend-type Grape
  Fruit
  (subtotal [item]
    (* 178 (:qty item))))

(extend-type Orange
  Fruit
  (subtotal [item]
    (* 98 (:qty item))))

;;; 'coupon' is the function returing a 'reify' of subtotal. This is
;;; when someone uses a coupon ticket, some fruits price down 25%.

(defn coupon [item]
  (reify Fruit
    (subtotal [_]
      (int (* 0.75 (subtotal item))))))

;;; Example: To compute the total when someone bought 10 oranges,
;;;  15 bananas and 10 grapes using a coupon.
;;; foo=> (apply +  (map subtotal [(Orange. 10) (Banana. 15) (coupon (Grape. 10))]))
;;; 4685            ; (apply + '(980 2370 1335))
;;; foo=> 

;;; This is a library for the shopping result.

(defrecord Banana [qty])
(defrecord Grape  [qty])
(defrecord Orange [qty])

;;; 'subtotal' differ from each fruit.

(defprotocol Fruit
  (subtotal [item]))

(extend-type Banana
  Fruit
  (subtotal [item]
    (* 158 (:qty item))))

(extend-type Grape
  Fruit
  (subtotal [item]
    (* 178 (:qty item))))

(extend-type Orange
  Fruit
  (subtotal [item]
    (* 98 (:qty item))))

;;; 'coupon' is the function returing a 'reify' of subtotal. This is
;;; when someone uses a coupon ticket, some fruits price down 25%.

(defn coupon [item]
  (reify Fruit
    (subtotal [_]
      (int (* 0.75 (subtotal item))))))

;;; Example: To compute the total when someone bought 10 oranges,
;;;  15 bananas and 10 grapes using a coupon.
;;; foo=> (apply +  (map subtotal [(Orange. 10) (Banana. 15) (coupon (Grape. 10))]))
;;; 4685            ; (apply + '(980 2370 1335))
;;; foo=>