Clojure bootcamp, 20.8.2014, muistiinpanot / hands-on

working-with-data.clj

(ns working-with-data
  (:require [metosin.dataset.pizzas :refer [pizzas]]))

(conj pizzas {:name "Speciale"})

; v1
(filter (fn [pizza]
          (if (< (get pizza :price) 8)
            true))
        pizzas)
;; => ({:toppings {:ham 3, :pineaple 2, :blue-cheese 1}, :name "Americana", :price 7.9} {:toppings {:mozarella 4, :tomato 3}, :name "Margherita", :price 7.2})

; v2
(filter (fn [pizza]
          (< (get pizza :price) 8))
        pizzas)
;; => ({:toppings {:ham 3, :pineaple 2, :blue-cheese 1}, :name "Americana", :price 7.9} {:toppings {:mozarella 4, :tomato 3}, :name "Margherita", :price 7.2})

; v3
(filter (fn [pizza]
          (< (:price pizza) 8))
        pizzas)

; v4
(filter (fn [{price :price}]
          (< price 8))
        pizzas)
;; => ({:toppings {:ham 3, :pineaple 2, :blue-cheese 1}, :name "Americana", :price 7.9} {:toppings {:mozarella 4, :tomato 3}, :name "Margherita", :price 7.2})

; v5
(filter #(< (:price %) 8) pizzas)
;; => ({:toppings {:ham 3, :pineaple 2, :blue-cheese 1}, :name "Americana", :price 7.9} {:toppings {:mozarella 4, :tomato 3}, :name "Margherita", :price 7.2})



; v1
(map (fn [pizza]
       (:name pizza))
     pizzas)
;; => ("Alla Pollo" "Americana" "Margherita")

; v2
(map :name pizzas)
;; => ("Alla Pollo" "Americana" "Margherita")

(def numeroita (range 100))
(def isompia (map (fn [n]
                    (println n)
                    (inc n))
                  numeroita))
;; => #'working-with-data/isompia



; acc = accumulator
(reduce (fn [acc pizza]
          (+ acc (:price pizza)))
        0
        pizzas)
;; => 23.400000000000002
;; => 0




; v1
(map clojure.string/upper-case (map :name (filter (fn [{price :price}]
                                                    (< price 8))
                                                  pizzas)))
;; => ("AMERICANA" "MARGHERITA")

(macroexpand-1 '(->> pizzas
                     (filter (fn [{price :price}]
                               (< price 8)))
                     (map :name)
                     (map clojure.string/upper-case)))
;; => (map clojure.string/upper-case (map :name (filter (fn [{price :price}] (< price 8)) pizzas)))
;; => ("AMERICANA" "MARGHERITA")
;; => ("AMERICANA" "MARGHERITA")

; v n+1
; fn-> threading macro
(filter (fn-> :price (< 8)) pizzas)

(doall isompia)
;; => nil
;; => 33
;; => 32
;; => 31
;; => 1
;; => 1



(defn second [[_ x]]
  x)

(def a {:foo 1})
(a :foo)
;; => 1
;; => 1
;; => 1
;; => nil

;; Mitä tapahtui kun ei avainta..
(< (get {} :price) 8)
;; => true
;; => 0
;; => nil