数学计算, 用于结果 Number为null 时无法计算的问题

    函数 案例 结果
    scale2(makeup: Boolean = true): String val a: String = 12.13124123.scale2()
    val b: String = 12.10.scale2()
    val c: String = 12.00.scale2()
    val d: String = 12.456.scale2()
    val a1: String = 12.13124123.scale2(false)
    val b1: String = 12.10.scale2(false)
    val c1: String = 12.00.scale2(false)
    val d1: String = 12.456.scale2(false)    		 a = 12.13
    b = 12.10
    c = 12.00
    d = 12.46
    a1 = 12.13
    b1 = 12.1
    c1 = 12
    d1 = 12.46
    add(num: Double): Double val add: Double = 1.1.add(3.0) add = 1.1 + 3.0
    subtract(num: Double): Double val subtract: Double = 1.1.subtract(3.0) subtract = 1.1 - 3.0
    multiply(num: Double): Double val multiply: Double = 1.1.multiply(3.0) multiply = 1.1 * 3.0
    divide(num: Double): Double val divide: Double = 1.1.divide(3.0) divide = 1.1 / 3.0