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clojure 初学习

Syntas
Forms
Control Flows
Data Structures
When should you use a list and when should you use a vector?

Syntas

(+ 1 2 3)

Forms

(+ 1 2 3)

Control Flows

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(if boolean-form
   then-form
   optional-else-form)

(if true  (do
          (println "Success!")
          "By Zeus's hammer!")
          (do (println "Failure!")
          "By Aquaman's trident!"))
; => Success!; => "By Zeus's hammer!"

when

1 2	(when true (println "Success!") "abra cadabra") ; => Success!; => "abra cadabra"

Data Structures

Number
934/5
Strings

1	"Lord Voldemort""\"He who must not be named\"""\"Great cow of Moscow!\" - Hermes Conrad"

Maps
{ }
{:first-name "Charlie" :last-name "McFishwich"}
Keywords

1 2	(:a {:a 1 :b 2 :c 3}); => 1 (get {:a 1 :b 2 :c 3} :a); => 1

Vectors

[3 2 1]
(get [3 2 1] 0); => 3
(vector "creepy" "full" "moon"); => ["creepy" "full" "moon"]
(conj [1 2 3] 4); => [1 2 3 4]

Lists

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(1 2 3 4); => (1 2 3 4)
(nth '(:a :b :c) 0); => :a(nth '(:a :b :c) 2); => :c
(list 1 "two" {3 4}); => (1 "two" {3 4})

When should you use a list and when should you use a vector?

A good rule of thumb is that if you need to easily add items to the beginning of a sequence or if you’re writing a macro, you should use a list.
Otherwise,you should use a vector.

Sets

#{"kurt vonnegut" 20 :icicle}
(hash-set 1 1 2 2); => #{1 2}
(conj #{:a :b} :b); => #{:a :b}
(set [3 3 3 4 4]); => #{3 4}

(contains? #{:a :b} :a)
; => true
(contains? #{:a :b} 3)
; => false
(contains? #{nil} nil)
; => true

(:a #{:a :b}); => :a

(get #{:a :b} :a); => :a
(get #{:a nil} nil); => nil
(get #{:a :b} "kurt vonnegut"); => nil

Functions

➊ (defn too-enthusiastic➋
"Return a cheer that might be a bit too enthusiastic"➌
[name]➍
(str "OH. MY. GOD! " name " YOU ARE MOST DEFINITELY LIKE THE BEST "     "MAN SLASH WOMAN EVER I LOVE YOU AND WE SHOULD RUN AWAY SOMEWHERE"))

;;use this functions
(too-enthusiastic "Zelda")
; => "OH. MY. GOD! Zelda YOU ARE MOST DEFINITELY LIKE THE BEST MAN SLASH WOMAN   EVER I LOVE YOU AND WE SHOULD RUN AWAY SOMEWHERE"

(defn multi-arity  ;; 3-arity arguments and body
([first-arg second-arg third-arg]     (do-things first-arg second-arg third-arg))  ;; 2-arity arguments and body
([first-arg second-arg] (do-things first-arg second-arg))  ;; 1-arity arguments and body
([first-arg]     (do-things first-arg)))

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;; Return the first element of a collection
(defn my-first  [[first-thing]] ; Notice that first-thing is within a vector  first-thing)
(my-first ["oven" "bike" "war-axe"]); => "oven"

Destructuring

(defn announce-treasure-location➊    [{lat :lat lng :lng}]
(println (str "Treasure lat: " lat))
(println (str "Treasure lng: " lng)))

(announce-treasure-location {:lat 28.22 :lng 81.33})   ; => Treasure lat: 100   ; => Treasure lng: 50

Anonymous Functions

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(fn [param-list]  function body)

#(* % 3)

clojure的入门如此的复杂，而构成是如此的简单，对于一个简单的执行
(function arg arg arg) 就是一段执行的函数。使用do作为将一堆函数放在一起，形成一个form
使用Destructuring 进行参数的结构。
clojure的数据类型又是如此复杂。

2024-11-05 该篇文章被 apple115 打上标签: lang