Kotlin list extension function-CodePudding

I have an extension function shown below

infix fun List<Int>.sumList(that: List<Int>) =
    this.zip(that, Int::plus)

I am now trying to make this extension function generic so that it works on list of integers as well as float and double.

listOf(1,2,3).sumList(listOf(10,20,30)) gives me [11, 22, 33]

Below is my attempt of writing the same extension function using generics

inline infix fun <reified T: Number> List<T>.sumListNew(that: List<T>): List<T> = when {
    T is Double -> this.zip(that, Double::plus)
    else -> this.zip(that, Int::plus)
}

However I am getting compiler error at T saying type parameter is not an expression. Can someone help me resolve this error and also reason for getting this error?

CodePudding user response：

Perhaps you may do it this way by having one sum method and just overriding the plus operator for Number:

operator fun Number.plus(a : Number) : Number{
    return when(this::class){
        Int::class -> this.toInt()   a.toInt()
        Double::class -> this.toDouble()   a.toDouble()
        else -> error("Data Type not found!")
    }
}

inline infix fun <reified T: Number> List<T>.sumListNew(that: List<T>): List<T>{
    return this.zip(that,Number::plus) as List<T>
}