Swift学习(一):自定义运算符 operator

自定义运算符 operator

  • 自定义运算符仅能包含这些字符:

/ = - + * % < >!& | ^。~

  • 运算符位置:

前置运算符 prefix
中间运算符 infix
后置运算符 postfix

  • 运算符其他配置
结合性        `associativity`
可取值范围   `left`,`right`和`none`

优先级        `precedence`
可取值范围    `0~255`

系统内置运算符结合性质及优先级
    求幂相关(无结合,优先级160)
       `<<` 按位左移(Bitwise left shift)
        `>>` 按位右移(Bitwise right shift)
 
    乘除法相关(左结合,优先级150)
        * 乘
        / 除
        % 求余
        &* 乘法,忽略溢出( Multiply, ignoring overflow)
        &/ 除法,忽略溢出(Divide, ignoring overflow)
        &% 求余, 忽略溢出( Remainder, ignoring overflow)
        & 位与( Bitwise AND)
 
    加减法相关(左结合, 优先级140)
        + 加
        - 减
        &+ Add with overflow
        &- Subtract with overflow
        | 按位或(Bitwise OR )
        ^ 按位异或(Bitwise XOR)
 
    Range (无结合,优先级 135)
        .. 半闭值域 Half-closed range
        ... 全闭值域 Closed range
 
    类型转换 (无结合,优先级 132)
        is 类型检查( type check)
        as 类型转换( type cast)
        <= 小于等于
        >大于
        >= 大于等于
        == 等于
        != 不等
        === 恒等于
        !== 不恒等
        ~= 模式匹配( Pattern match)
 
    合取( Conjunctive) (左结合,优先级 120)
        && 逻辑与(Logical AND)
 
    析取(Disjunctive) (左结合,优先级 110)
        || 逻辑或( Logical OR)
 
    三元条件(Ternary Conditional )(右结合,优先级 100)
        ?: 三元条件 Ternary conditional
 
    赋值 (Assignment) (右结合, 优先级 90)
        = 赋值(Assign)
        *= Multiply and assign
        /= Divide and assign
        %= Remainder and assign
        += Add and assign
        -= Subtract and assign
        <<= Left bit shift and assign
        = Right bit shift and assign
        &= Bitwise AND and assign
        ^= Bitwise XOR and assign
        |= Bitwise OR and assign
        &&= Logical AND and assign
        ||= Logical OR and assign

范例:

// 前置:返回2的n次方
prefix operator  ^ {}

prefix func ^ (var vector: Double) -> Double {
    return pow(2, vector)
}

println(^5)  // 32.0

// 后置:返回2次方
postfix operator  ^ {}

postfix func ^ (var vector: Int) -> Int {
    return vector * vector
}

println(5^)  // 25


//中间:计算N的M次方,左结合,优先级为255
infix operator ^^ {associativity left precedence 255}

func ^^(left: Double, right: Double) -> Double {
    return pow(left, right)
}

println(2 ^^ 10 - 2 ^^ 3)  // 1024 - 8 = 1016

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