In my kotlin code i am getting Type mismatch(inferred type is Int but Boolean was expected) error.
fun main(args: Array<String>) {
var i = args.size
while (i--){
println(args[i])
}
}
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1What is unclear? while expects a boolean expression. i-- is of type Int.JB Nizet– JB Nizet2017-06-01 06:52:44 +00:00Commented Jun 1, 2017 at 6:52
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4 Answers
You have to provide a Boolean value as the argument of while. There's no auto-casting of Int to Boolean in Kotlin.
So you can't do while(i--), but you can, for example, do while(i-- != 0) or while(i-- > 0).
Comments
while (x > 0) { x-- } do { val y = retrieveData() } while (y != null) // y is visible here!
Comments
First of all, args.size is +1 greater than the last element's index in the array. Therefore, you must subtract 1 from the resulting value: args.size-1 (or you can use i-1). Additionally, just like using an if-statement in Kotlin, a while-loop requires a Boolean expression, i.e. while(true/false) {...}.
fun methodWith(args: Array<String>) {
var i = args.size - 1 // args.size = 2
while (i >= 0) {
println(args[i])
i -= 1
}
}
fun main() {
val strings = arrayOf("Kotlin","Java","Python")
methodWith(strings)
}
You can also declare a Boolean property for a while's condition.
fun methodWith(args: Array<String>) {
var i = args.size // args.size = 3
var bool: Boolean = true
while (bool) {
println(args[i-1]) // -1
i -= 1
if (i <= 0) bool = false
}
}
fun main() {
val strings = arrayOf("Kotlin","Java","Python")
methodWith(strings)
}
Result:
Python
Java
Kotlin
Comments
while expects a boolean (true/false), you give an integer (i-1). correct code could be:
fun main(args: Array<String>) {
var i = args.size
while (i>=0){
println(args[i])
i--
}
}
