com.rpl.specter-example

specter.example.clj

(use 'com.rpl.specter)

;; 过滤元素
(filter odd? [1 2 3 4 5 6]) ;; (1 3 5)
(select [ALL odd?] [1 2 3 4 5 6]) ;; [1 3 5]

;; 选择奇数位的元素
(select [INDEXED-VALS (comp odd? first) LAST] [:a :b :c :d :e]) ;; [:b :d]

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;; 复杂选择
;; 此示例输入是一条常见的hiccup数据，其中包含网站列表，每个网站有名称、网址、成立日期及简介内容。
;; 我们希望将此输入转换为clojure数据结构，即提取名称、网址、成立日期及简介再转换为map队列输出
(def root {:content
           [{:type :element,
             :attrs nil,
             :tag :h3,
             :content
             [{:type :element,
               :attrs
               {:title "Permanent Link to Bcelebrated",
                :href
                "http://www.thedigitalbeyond.com/online-services-list/bcelebrated/",
                :rel "bookmark"},
               :tag :a,
               :content ["Bcelebrated"]}]}
            "\n"
            {:type :element,
             :attrs
             {:href "http://www.bcelebrated.com",
              :name "Link to Bcelebrated"},
             :tag :a,
             :content ["www.bcelebrated.com"]}
            {:type :element,
             :attrs nil,
             :tag :p,
             :content
             [{:type :element,
               :attrs nil,
               :tag :strong,
               :content ["Founded: "]}
              "July, 2009"]}
            {:type :element,
             :attrs nil,
             :tag :p,
             :content
             ["Bcelebrated enables members to create a multi-media website that will become their autobiographical memorial site when the time comes."]}
            {:type :element,
             :attrs nil,
             :tag :h3,
             :content
             [{:type :element,
               :attrs
               {:title "Permanent Link to Boxego",
                :href
                "http://www.thedigitalbeyond.com/online-services-list/boxego/",
                :rel "bookmark"},
               :tag :a,
               :content ["Boxego"]}]}
            "\n"
            {:type :element,
             :attrs
             {:href "http://www.boxego.com",
              :name "Link to Boxego"},
             :tag :a,
             :content ["www.boxego.com"]}
            {:type :element,
             :attrs nil,
             :tag :p,
             :content
             [{:type :element,
               :attrs nil,
               :tag :strong,
               
               :content ["Founded: "]}
              "2013"]}
            {:type :element,
             :attrs nil,
             :tag :p,
             :content
             ["Boxego is a private journal that can be shared privately and socially, now and in the future."]}]})

;; 取标题 h3
(select [:content ALL (pred #(= :h3 (:tag %))) :content ALL :content FIRST] root) ;; ["Bcelebrated" "Boxego"]

;; 取网站链接 
(select [:content ALL (pred #(= :a (:tag %))) :attrs :href] root) ;; ["http://www.bcelebrated.com" "http://www.boxego.com"]

;; 取时间与文章描述
(select [:content ALL (pred #(= :p (:tag %))) :content LAST] root) ;; ["July, 2009" "Bcelebrated enables members to create a multi-media website that will become their autobiographical memorial site when the time comes." "2013" "Boxego is a private journal that can be shared privately and socially, now and in the future."]

;; 同时取上面三类内容，使用multi-path同时选择多个路径
(def paths [[(pred #(= :h3 (:tag %))) :content ALL :content FIRST]
            [(pred #(= :a (:tag %))) :attrs :href]
            [(pred #(= :p (:tag %))) :content LAST]])

(select [:content ALL (apply multi-path paths)] root) ;; ["Bcelebrated" "http://www.bcelebrated.com" "July, 2009" "Bcelebrated enables members to create a multi-media website that will become their autobiographical memorial site when the time comes." "Boxego" "http://www.boxego.com" "2013" "Boxego is a private journal that can be shared privately and socially, now and in the future."]

;; 下面我们来看如何转换成我们期望的map集合的结构。这里要用到transform
(->>
 (select [:content ALL (apply multi-path paths)] root)
 (partition 3)
 (transform [ALL] (fn [[title url description]] {:title title :url url :description description}))) ;; ({:title "Bcelebrated", :url "http://www.bcelebrated.com", :description "July, 2009"} {:title "Bcelebrated enables members to create a multi-media website that will become their autobiographical memorial site when the time comes.", :url "Boxego", :description "http://www.boxego.com"})


;; recursion
(def tree [1 [2 [[3]] 4] [[5] 6] [7] 8 [[9]]])

(def TREE-VALUES
  (recursive-path [] p
                  (if-path vector?
                           [ALL p]
                           STAY)))

(select TREE-VALUES [1 [2 [3 4] 5] [[6]]]) ;; [1 2 3 4 5 6]