条件にあてはあまるところで止める

isContinueReduce.kt

var isContinue:Boolean = true

val list  = arrayOf("hello", "good", "text", "hello2", "text2")
val result =   list.asSequence().takeWhile{isContinue}.reduce {s1, s2->
    if(s1.length == 4 && s2.length == 4) {
        isContinue = false
        return@reduce s1+s2
    }
    s2
}
if(isContinue) {
    println("見つかりませんでした")
} else {
    println(result)
}


// Output
// goodtext