When With Ranges

Sometimes you need to check if a value falls within a range rather than matching specific values. The when expression supports this using the in keyword combined with ranges.

fun main() {
    val score = 85
    
    val grade = when (score) {
        in 90..100 -> "A"
        in 80..89 -> "B"
        in 70..79 -> "C"
        in 60..69 -> "D"
        else -> "F"
    }
    
    println(grade)  // Prints: B
}

The in keyword checks if the value exists within the specified range. Here, 85 falls within 80..89, so the grade is "B". This is much cleaner than writing score >= 80 && score <= 89 for each condition.

You can also combine ranges with specific values in the same when expression:

fun main() {
    val age = 17
    
    val category = when (age) {
        0 -> "Newborn"
        in 1..12 -> "Child"
        in 13..19 -> "Teenager"
        else -> "Adult"
    }
    
    println(category)  // Prints: Teenager
}

Ranges make your code more readable when dealing with continuous numeric conditions, which is common in grading systems, age categories, and similar scenarios.