Docker下安装 Clojure

Docker环境下Clojure

1. 搜索 Clojure 镜像,下载，并在命令行下启动镜像

> docker search clojure
> docker pull clojure
> docker run -i -t clojure /bin/bash

2. 使用 Clojure 的 REPL(standing for Read-Eval-Print Loop)
   当进入 Clojure 下的命令行模式下：

> lein new hello-world
> cd hello-world/
> lein repl                    # 启动 repl 环境

执行最后一句时，会自动安装一些东西，并且进入 REPL 环境.如下所示：

root@5d542fdfabba:/tmp/hello-world# lein repl
Retrieving org/clojure/clojure/1.9.0/clojure-1.9.0.pom from central
Retrieving org/clojure/spec.alpha/0.1.143/spec.alpha-0.1.143.pom from central
Retrieving org/clojure/core.specs.alpha/0.1.24/core.specs.alpha-0.1.24.pom from central
Retrieving org/clojure/clojure/1.9.0/clojure-1.9.0.jar from central
Retrieving org/clojure/core.specs.alpha/0.1.24/core.specs.alpha-0.1.24.jar from central
Retrieving org/clojure/spec.alpha/0.1.143/spec.alpha-0.1.143.jar from central
nREPL server started on port 37573 on host 127.0.0.1 - nrepl://127.0.0.1:37573
REPL-y 0.4.3, nREPL 0.5.3
Clojure 1.9.0
OpenJDK 64-Bit Server VM 1.8.0_181-8u181-b13-2~deb9u1-b13
    Docs: (doc function-name-here)
          (find-doc "part-of-name-here")
  Source: (source function-name-here)
 Javadoc: (javadoc java-object-or-class-here)
    Exit: Control+D or (exit) or (quit)
 Results: Stored in vars *1, *2, *3, an exception in *e

hello-world.core=>

---

语法特性说明来自于下面链接，这里只列举了一些我看代码用到了一些语法：

Clojure API

一些语法特性：

->

(-> x & forms)  // x 作为 forms 的第二个参数进行处理

=> (-> 1 (+ 3) (/ 2))  // (/ (+ 1 3) 2 
2

->>

(->> x & forms)  // x 作为 forms 的最后一个参数进行处理

=> (->> 1 (+ 3) (/ 2))
1/2

assoc

(assoc map key val)
(assoc map key val & kvs)  //添加后面的 kv （存在就更新）返回一个新的 map

=> (assoc {:key1 "old value1" :key2 "value2"}:key1 "value1" :key3 "value3")
{:key1 "value1", :key2 "value2", :key3 "value3"}
=> (assoc [1 2 3] 0 10)    //替换index 为 0 的value为 10
[10 2 3]
=> (assoc [1 2 3] 3 10)
[1 2 3 10]

apply

(apply f args)
(apply f x args)
(apply f a b c d & args)  //应用由 f 构造的匿名方法，参数是后面的各个项的拆分

=> (max [1 2 3])
[1 2 3]
=> (apply max [1 2 3])
3
=> (apply max 1 2 3)
IllegalArgumentException Don't know how to create ISeq from: java.lang.Long  clojure.lang.RT.seqFrom (RT.java:550)
=> (max 1 2 3)
3

let

(let [bindings*] exprs*)   //在bingings中进行数据绑定。然后执行表达式expres

=> ( let [a 1 b 2] (+ a b))
3
=> (let [c (+ 1 2) [d e] [5 6]] (-> (+ d e) (- c)))
8

if-let

(if-let bindings then)(if-let bindings then else & oldform)

(defn if-let-demo [arg]
  (if-let [x arg]
    "then"
    "else"))

(if-let-demo 1) ; anything except nil/false
;;=> "then"
(if-let-demo nil)
;;=> "else"
(if-let-demo false)
;;=> "else"

merge

(merge & maps) 返回一个map，后面的 maps 添加到前面的map

=> (merge {:a 1 :b 2 :c 3} {:b 9 :d 4})
{:a 1, :b 9, :c 3, :d 4}

str

(str)
(str x)
(str x & ys) 拼接字符串

=> (str "L" 5 "a")
"L5a"

cond->

(cond-> expr & clauses) //

=> (defn say [n]
     (cond-> nil
       (divisible-by? 3 n) (str "Fizz")
       (divisible-by? 5 n) (str "Buzz")
       :always             (or (str n))))
#'user/say

=> (say 1)
"1"

=> (say 3)
"Fizz"

=> (say 5)
"Buzz"

=> (say 15)
"FizzBuzz"

select-keys

(select-keys map keyseq)

user=> (select-keys {:a 1 :b 2} [:a])
{:a 1}
user=> (select-keys {:a 1 :b 2} [:a :c])
{:a 1}
user=> (select-keys {:a 1 :b 2 :c 3} [:a :c])
{:c 3, :a 1}