Challenge 1: A Value Class for Type Safety — Solution

@JvmInline
value class Meters(val value: Double)

@JvmInline
value class Feet(val value: Double)

fun metersToFeet(m: Meters): Feet = Feet(m.value * 3.28084)

fun main() {
    val distance = Meters(10.0)
    val converted = metersToFeet(distance)
    println("${distance.value}m = ${converted.value}ft")

    // val wrong = metersToFeet(Feet(5.0))   // Compile error: Feet is not Meters
}

/*
Output:
10.0m = 32.8084ft

Notes:
- Meters and Feet both wrap a Double, but the compiler treats them as
  completely distinct types — metersToFeet(Meters) only accepts a
  Meters value, so passing a Feet(5.0) by mistake is caught at compile
  time, not discovered later as a silently wrong unit conversion.
- At runtime, both Meters and Feet are erased to plain Double values in
  most cases (per @JvmInline), so this safety comes with no extra
  allocation or performance cost compared to just using raw Double
  everywhere and hoping not to mix them up.
*/