Kotlin pre and post conditions

inc.kt

// Out-of-the-box require() stmts
fun increment1(x: Int): Int {
  require(x > 0) { "value must be positive" }
  return (x + 1).also { require(it > 0) { "result is positive" } }
}

// Consolidate the post also/require() stmts into ensure() 
fun increment2(x: Int): Int {
  require(x > 0) { "value must be positive" }
  return (x + 1).ensure({ it > 0 }) { "result is positive" }
}