基本数据类型 #

一、数据类型概述 #

Clojure是动态类型语言，数据类型在运行时确定。Clojure提供了丰富的数据类型，同时与Java类型系统无缝集成。

1.1 类型分类 #

类别	类型	示例
数字	整数、浮点、比率、大数	`42`, `3.14`, `1/3`
布尔	true、false	`true`, `false`
空值	nil	`nil`
字符串	String	`"hello"`
字符	Character	`\a`, `\newline`
关键字	Keyword	`:name`
符号	Symbol	`x`, `my-var`

二、数字类型 #

2.1 整数 #

clojure

42

-17

0

2r1010

8r77

16rFF

36rZ

整数类型：

类型	范围	示例
Long	-2^63 到 2^63-1	`42`
BigInt	任意精度	`42N`

clojure

(class 42)

(class 42N)

2.2 浮点数 #

clojure

3.14

-0.5

1.0e10

6.022e23

浮点类型：

类型	说明	示例
Double	64位浮点	`3.14`
BigDecimal	任意精度	`3.14M`

clojure

(class 3.14)

(class 3.14M)

2.3 比率 #

Clojure原生支持有理数：

clojure

1/3

22/7

(/ 1 3)

(+ 1/3 1/4)

clojure

(class 1/3)

比率运算保持精度：

clojure

(+ 1/3 1/3 1/3)

(* 1/3 3)

2.4 算术运算 #

clojure

(+ 1 2 3)

(- 10 3)

(* 2 3 4)

(/ 10 2)

(/ 10 3)

(quot 10 3)

(rem 10 3)

(mod 10 3)

(inc 5)

(dec 5)

2.5 数学函数 #

clojure

(max 1 5 3 2)

(min 1 5 3 2)

(abs -5)

(Math/pow 2 10)

(Math/sqrt 16)

(Math/round 3.7)

2.6 比较运算 #

clojure

(= 1 1)

(= 1 1.0)

(== 1 1.0)

(not= 1 2)

(< 1 2 3)

(<= 1 1 2)

(> 3 2 1)

(>= 3 3 2)

三、布尔类型 #

3.1 布尔值 #

clojure

true

false

(class true)

3.2 逻辑运算 #

clojure

(and true true)

(and true false)

(and true true true)

(or false true)

(or false false)

(not true)

(not false)

3.3 真值判断 #

在Clojure中，只有 false 和 nil 是逻辑假：

clojure

(boolean true)

(boolean false)

(boolean nil)

(boolean 0)

(boolean "")

(boolean [])

(boolean "hello")

3.4 条件判断函数 #

clojure

(true? true)

(true? false)

(false? false)

(false? nil)

(nil? nil)

(nil? false)

(some? nil)

(some? "hello")

四、nil类型 #

4.1 nil的含义 #

nil 表示"无值"或"空"：

clojure

nil

(class nil)

4.2 nil的使用场景 #

clojure

(defn find-user [id]
  (if (= id 1)
    {:id 1 :name "Alice"}
    nil))

(find-user 1)

(find-user 2)

4.3 nil处理 #

clojure

(nil? nil)

(some? nil)

(if nil "yes" "no")

(when nil "yes")

4.4 nil与空集合 #

clojure

(empty? nil)

(empty? [])

(empty? "")

(seq nil)

(seq [])

五、字符串类型 #

5.1 字符串字面量 #

clojure

"Hello, World!"

"Line 1\nLine 2"

"Tab\there"

"Quote: \"Hello\""

"Backslash: \\"

clojure

(class "hello")

5.2 字符串操作 #

clojure

(str "Hello" " " "World")

(str 42)

(str :keyword)

(str nil)

(count "hello")

(subs "hello world" 0 5)

(subs "hello world" 6)

5.3 字符串函数 #

clojure

(require '[clojure.string :as str])

(str/upper-case "hello")

(str/lower-case "HELLO")

(str/capitalize "hello world")

(str/trim "  hello  ")

(str/triml "  hello  ")

(str/trimr "  hello  ")

(str/split "a,b,c" #",")

(str/join ["a" "b" "c"])

(str/join "," ["a" "b" "c"])

(str/replace "hello world" "world" "Clojure")

(str/replace "hello 123" #"\d+" "NUM")

5.4 字符串判断 #

clojure

(str/starts-with? "hello world" "hello")

(str/ends-with? "hello.txt" ".txt")

(str/includes? "hello world" "wor")

(str/blank? "")

(str/blank? "   ")

(str/blank? nil)

六、字符类型 #

6.1 字符字面量 #

clojure

\a

\A

\newline

\space

\tab

\u03A9

\o41

clojure

(class \a)

6.2 字符操作 #

clojure

(int \a)

(char 97)

(str \a \b \c)

(char-escape-string \newline)

6.3 字符判断 #

clojure

(Character/isDigit \5)

(Character/isLetter \a)

(Character/isWhitespace \space)

(Character/isUpperCase \A)

(Character/isLowerCase \a)

七、类型判断 #

7.1 class函数 #

clojure

(class 42)

(class 3.14)

(class "hello")

(class :keyword)

(class [1 2 3])

(class {:a 1})

7.2 type函数 #

clojure

(type 42)

(type 42N)

(type 3.14M)

7.3 类型谓词 #

clojure

(integer? 42)

(integer? 3.14)

(float? 3.14)

(ratio? 1/3)

(number? 42)

(number? "42")

(string? "hello")

(char? \a)

(boolean? true)

(nil? nil)

(keyword? :name)

(symbol? 'x)

(coll? [1 2 3])

(list? '(1 2 3))

(vector? [1 2 3])

(map? {:a 1})

(set? #{1 2 3})

八、类型转换 #

8.1 数字转换 #

clojure

(int 3.14)

(long 3.14)

(float 42)

(double 42)

(bigint 42)

(bigdec 3.14)

(num 42)

(rationalize 3.5)

8.2 字符串转换 #

clojure

(str 42)

(str 3.14)

(str :keyword)

(str \a \b \c)

(format "Hello, %s! You have %d messages." "Alice" 5)

8.3 解析字符串 #

clojure

(Integer/parseInt "42")

(Long/parseLong "42")

(Float/parseFloat "3.14")

(Double/parseDouble "3.14")

(BigDecimal. "3.14159265359")

(BigInteger. "12345678901234567890")

九、相等性 #

9.1 = vs == #

clojure

(= 1 1)

(= 1 1.0)

(== 1 1.0)

(= "hello" "hello")

(= [1 2 3] [1 2 3])

(= {:a 1} {:a 1})

(identical? "hello" "hello")

9.2 值相等 #

Clojure的 = 比较值相等：

clojure

(= [1 2 3] [1 2 3])

(= {:a 1 :b 2} {:b 2 :a 1})

(= #{1 2 3} #{3 2 1})

9.3 引用相等 #

clojure

(identical? 1 1)

(let [v [1 2 3]]
  (identical? v v))

十、总结 #

Clojure基本数据类型要点：

类型	特点
数字	支持整数、浮点、比率、大数
布尔	只有true和false
nil	表示空值，逻辑假
字符串	Java String，不可变
字符	Java Character

类型判断常用函数：

class / type：获取类型
integer?、string? 等：类型谓词
=：值相等
==：数字相等

下一步，让我们学习关键字与符号！