Float.isNaN 'receiver type mismatch' error in Kotlin

I am new to Kotlin and having an issue with Kotli'ns built-in FLoat.isNaN and Double.isNaN functions. When using the Float.isNaN function to test for NaN equalt of a float arraylist I receive the error:

Unresolved reference. None of the following candidates is applicable because of receiver type mismatch:

public inline fun Double.isNaN(): Boolean defined in kotlin public

inline fun Float.isNaN(): Boolean defined in kotlin

Pseudocode is listed below, appreciate any help:

var scores = arrayListOf<Float>()
val todaysResult = scores[0]
if(Float.isNaN(todaysResult)) {
    todayResultNumericTextView!!.text = "-"
} else {
    todayResultNumericTextView!!.text = Math.round(todaysResult).toString() + "%"
}

Solution

isNaN is an extension function on Float and Double (not a "static" method, unlike in Java!) This means you must invoke it with the value as the receiver.

fun Double.isNaN(): Boolean
fun Float.isNaN(): Boolean

Instead of

Float.isNaN(todaysResult)

you want

todaysResult.isNaN()

This is also indicated by the error message:

public inline fun Double.isNaN(): Boolean defined in kotlin
public inline fun Float.isNaN(): Boolean defined in kotlin

The syntax Float.isNaN() indicates that this function takes a receiver of type Float.