chapter2.kt

class Rectangle(val height: Int, val width: Int) {
    val isSquare: Boolean
        get() {
            return height == width
        }
}

val rectangle = Rectangle(41, 43)
println(rectangle.isSquare)

interface Expr
class Num(val value: Int): Expr
class Sum(val left: Expr, val right: Expr): Expr

fun evalWithLogging(e: Expr): Int =
        when (e) {
            is Num -> {
                println("num: ${e.value}")
                e.value
            }
            is Sum -> {
                val left = evalWithLogging(e.left)
                val right = evalWithLogging(e.right)
                println("sum: $left + $right")
                left + right
            }
            else -> throw IllegalArgumentException("Unknown expression")
        }

fun recognize(c: Char) = when (c) {
    in '0'..'9' -> "It's a digit"
    in 'a'..'z', in 'A'..'Z' -> "It's a letter"
    else -> "I don't know"
}

println(recognize('8'))
println(evalWithLogging(Sum(Sum(Num(1), Num(2)), Num(4))))