MathExprWithDivision.kt

sealed class MathExpression {
    fun eval(): Int = when (this) {
        is Addition -> left.eval() + right.eval()
        is Subtraction -> left.eval() - right.eval()
        is Division -> left.eval() / right.eval()
        is Number -> value
    }
}

data class Addition(val left: MathExpression, val right: MathExpression) : MathExpression()
data class Subtraction(val left: MathExpression, val right: MathExpression) : MathExpression()
data class Division(val left: MathExpression, val right: MathExpression) : MathExpression()
data class Number(val value: Int) : MathExpression()