medium-elvis3.kt

fun main() {
 // You can do this
 val assignment = null ?: false
    val fromBlock = when(assignment) {
        true -> true
        false -> null
    } ?: false
 // Or this
 val computed = if (fromBlock && assignment) { true } else { null }
 // see the outputs
 println("assignment $assignment")
 println("fromBlock $fromBlock")
 println("computed $computed")
 println("safe-output is ${computed ?: false}")
 
 // Never do this
 val b1 = nullableFun(true)
 val b2 = nullableFun(false)
 val b1b2 = b1 != b2 // this is confusing! are they Boolean or null?
 // Neither do this
 val b3 = b1 != b2 ?: false
 
 // Again, ok to do this
 val bok1 = b1 ?: true
 val bok2 = b2 ?: false
    
 //see the outputs...
 listOf(b1,b2,b1b2,b3,bok1,bok2).forEach { println(it) }
}

fun nullableFun(b: Boolean): Boolean? = if ( (0..1).shuffled().first() == 0) { b } else { null }