CurrencyOperatorOverloading.kt

data class Currency(val value: BigDecimal, val code: String) {
    constructor(v: Int, code: String): this(BigDecimal(v), code)
    fun convert(toCode: String): Currency {
        return Currency(convert(this, toCode), toCode)
    }
    private fun convert(fromCurrency: Currency, toCode: String): BigDecimal {
        //1 USD = 1.27082 CAD
        return if (fromCurrency.code == "USD" && toCode == "CAD") {
            fromCurrency.value * BigDecimal(1.27)
        } else if (fromCurrency.code == "CAD" && toCode == "USD") {
            fromCurrency.value / BigDecimal(1.27)
        } else {
            ...
        }
    }
    operator fun plus(that: Currency): Currency {
        println(convert(that, this.code))
        return Currency(convert(that, this.code) + this.value, this.code)
    }
    override fun toString(): String = "$value $code"
}