kotlin - 运算符重载 Kotlin
问题描述
我是 kotlin 的新手,我正在为我定义的自定义类处理运算符重载。该类称为“有理数”,表示有理数,例如 117/1098。类定义如下,我重载了一堆运算符,如加号、减号、时间等。但是我不确定我必须做什么来重载“in”运算符。
这是我的课:
data class Rational(val rational: String) {
private val numerator: BigInteger
private val denominator: BigInteger
init {
val splitted = rational.split("/")
numerator = splitted[0].toBigInteger()
denominator = when (splitted[1]) {
"0" -> throw Exception("not allowed")
else -> splitted[1].toBigInteger()
}
}
operator fun plus(number: Rational): Rational {
val gcm = denominator * number.denominator
val numerator = (gcm / denominator) * numerator + (gcm / number.denominator) * number.numerator
return Rational("$numerator/$gcm")
}
operator fun minus(number: Rational): Rational {
val gcm = denominator * number.denominator
val numerator = (gcm / denominator) * numerator - (gcm / number.denominator) * number.numerator
return Rational("$numerator/$gcm")
}
operator fun times(number: Rational): Rational {
val numerator = numerator * number.numerator
val denominator = denominator * number.denominator
return Rational("$numerator/$denominator")
}
operator fun div(number: Rational): Rational {
val numerator = numerator * number.denominator
val denominator = denominator * number.numerator
return Rational("$numerator/$denominator")
}
operator fun compareTo(number: Rational): Int {
val ratio = this.numerator.toFloat() / this.denominator.toFloat()
val numberRatio = number.numerator.toFloat() / number.denominator.toFloat()
if (ratio > numberRatio) {
return 1
} else if (ratio == numberRatio) {
return 0
}
return -1
}
operator fun unaryMinus(): Rational {
val inverseNumerator = -numerator
return Rational("$inverseNumerator/$denominator")
}
operator fun unaryPlus(): Rational {
return Rational("$numerator/$denominator")
}
operator fun rangeTo(end: Rational): Any {
var range: MutableList<Rational> = arrayListOf()
val startNumerator = this.numerator.toInt()
val endNumerator = end.numerator.toInt()
var index = 0
if (this.denominator == end.denominator) {
for (i in startNumerator..endNumerator) {
range.add(index, Rational("$i/$denominator"))
}
}
return range
}
operator fun contains(number: Rational): Boolean {
if (this.denominator % number.denominator == 0.toBigInteger()
&& this.numerator <= number.numerator) {
return true
}
return false
}
override fun toString(): String {
val gcd = numerator.gcd(denominator)
return if (gcd != null) {
val newNumerator = numerator / gcd
val newDenominator = denominator / gcd
"$newNumerator/$newDenominator"
} else {
"$numerator/$denominator"
}
}
}
infix fun Int.divBy(denominator: Int): Rational {
if (denominator == 0) {
throw Exception("denominator 0 not allowed")
}
return Rational("$this/$denominator")
}
infix fun Long.divBy(denominator: Long): Rational {
if (denominator == 0L) {
throw Exception("denominator 0 not allowed")
}
return Rational("$this/$denominator")
}
infix fun BigInteger.divBy(denominator: BigInteger): Rational {
if (denominator == 0.toBigInteger()) {
throw Exception("denominator 0 not allowed")
}
return Rational("$this/$denominator")
}
fun String.toRational(): Rational {
return Rational(this)
}
这是我的主体,显然仍然无法编译:
fun main() {
val half = 1 divBy 2
val third = 1 divBy 3
val twoThirds = 2 divBy 3
println(half in third..twoThirds) // this line does not compile beacause in operator is not defined for the class
}
我想我必须重写“rangeTo”运算符,但我不确定运算符原型。我有人可以请帮助我走上正轨吗?
解决方案
进行in
工作的方法是让third..twoThirds
调用返回具有方法的东西contains(Rational)
,这就是in
调用所转换的内容。
一种方法是在此处返回 a ClosedRange<Rational>
,如下所示:
operator fun rangeTo(end: Rational): ClosedRange<Rational> {
return object : ClosedRange<Rational> {
override val endInclusive: Rational = end
override val start: Rational = this@Rational
}
}
这对 施加了类型约束Rational
,因为ClosedRange
需要一个Comparable
实现来确定一个值是否属于它。您可以通过实现Comparable
接口来做到这一点,然后添加operator
到现有的compareTo
运算符(另外,重命名参数以匹配接口是一个很好的做法):
data class Rational(val rational: String) : Comparable<Rational> {
...
override operator fun compareTo(other: Rational): Int {
val ratio = this.numerator.toFloat() / this.denominator.toFloat()
val numberRatio = other.numerator.toFloat() / other.denominator.toFloat()
if (ratio > numberRatio) {
return 1
} else if (ratio == numberRatio) {
return 0
}
return -1
}
}
您还可以通过使用此实现来完全避免转换为浮点数,正如@gidds 在下面的评论中所建议的那样:
override operator fun compareTo(other: Rational): Int {
return (numerator * other.denominator - denominator * other.numerator).signum()
}
此外,您当前的contains
实现可能会被丢弃,因为您不再需要它,而且它的功能相当奇怪。
要在此处添加直接答案以外的其他内容:正如@Eugene Petrenko 在他们的回答中所建议的那样,添加几个构造函数而不是使用 a 的构造函数是实际的String
,例如一个需要两个Int
s 和一个需要两个BigIntegers
s .
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