CODEWITHSUNDEEP
kotlin
Zorgan
Zorgan

Reputation: 9143

2 operator overload functions of the same type

I'm doing Kotlin Koans's Operator Overloading exercise and am wondering how the compiler chooses which MyDate.plus() function to use:

import TimeInterval.*
import java.util.Calendar

data class MyDate(val year: Int, val month: Int, val dayOfMonth: Int)

enum class TimeInterval { DAY, WEEK, YEAR }

operator fun MyDate.plus(timeInterval: TimeInterval) = addTimeIntervals(timeInterval, 1)

class FullTimeInterval(val timeInterval: TimeInterval, val number: Int) 
operator fun TimeInterval.times(number: Int) = FullTimeInterval(this, number)

operator fun MyDate.plus(timeIntervals: FullTimeInterval) 
= addTimeIntervals(timeIntervals.timeInterval, timeIntervals.number)

fun task1(today: MyDate): MyDate {
    return today + YEAR + WEEK 
}

fun task2(today: MyDate): MyDate {
    return today + YEAR * 2 + WEEK * 3 + DAY * 5
}

Upvotes: 0

Views: 68

Answers (1)

Eugene Petrenko
Eugene Petrenko

Reputation: 4992

You have two classes: TimeInterval and FullTimeInterval and two overloaded functions: MyDate.plus(timeIntervals: TimeInterval) and MyDate.plus(timeIntervals: FullTimeInterval)

The compiler knows the type of the argument and it selects the closest function by the signature. The decision is made at the compilation time and depends on the computed types of the arguments.

You may find more information on that at https://jetbrains.github.io/kotlin-spec/#overload-resolution

Upvotes: 2

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