title: Kotlin: What do the unary plus/minus operators do on numbers?
body: <p>I've noticed in Kotlin that there are already defined <code>unaryPlus</code> and <code>unaryMinus</code> operators on all of the number types.</p>
  
  <p>What's the purpose of these operators? Are they in some way connected to the prefix forms of <code>inc</code> and <code>dec</code>?</p>