[Swift 官方教程]02 基础运算符

建议: 这部分理解看得懂就可以了, 不用作额外的练习

术语 (Terminology)

学一下英语:

🕐 加减乘除:

1 + 2
5 - 3
2 * 3
10.0 / 2.5

🕑 字符串拼接:

"hello, " + "world"

符号跟着被除数走:

9 % 4    // 1
-9 % 4   // -1

let x = 3
let y = -x
let z = -y

let n = +3

实际不会发生任何影响

举个例子:

var n = 1
n += 2

🕐 举个例子:

1 == 1
2 != 1
2 > 1
1 < 2
1 >= 1
2 <= 1

🕑 元组会逐个元素进行比较:

(1, "a") < (2, "c")

let x = 2
let b = true
let y = x + (b ? 10: 20)

let n = "root"
var s: String?
let m = s ?? n

获取区间内的离散数值

左闭右闭:

for i in 1...5 {
    print(i)
}

左闭右开:

for i in 1..<5 {
    print(i)
}

🕐 右穷尽:

let m = ["a", "b", "c", "d"]
for i in m[2...] {
    print(i)
}

🕑 左穷尽:

let m = ["a", "b", "c", "d"]
for i in m[...2] {
    print(i)
}

🕒 左穷尽右开:

let m = ["a", "b", "c", "d"]
for i in m[..<2] {
    print(i)
}

🕓 判断数字是否在区间中:

let range = ...5
print(range.contains(7))

let f = false
if !f {
    print("true")
}

let t = true
let f = false
if t && f {
    print("true")
} else {
    print("false")
}

let t = true
let f = false
if t || f {
    print("true")
} else {
    print("false")
}

上述逻辑运算符可以组合使用

可以使用 () 改变优先级或者语法美观