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@MishaelRosenthal
Created October 29, 2022 04:42
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type Digit = Int
def toDigits(i: Int) = i.toString.map(_.asDigit).reverse
def fromDigits(digits: Seq[Digit]) = digits.reverse.dropWhile(_ == 0).map(_.toString).reduce(_ + _).toInt
case class FullAdder(inCarry: Digit, i: Digit, j: Digit) {
val asDigits = toDigits(inCarry + i + j)
def sum() = asDigits(0)
def carry() = if(asDigits.length > 1) asDigits(1) else 0
}
def longAddition(x: Int, y: Int) = {
val xDigits = toDigits(x) ++ Seq(0)
val yDigits = toDigits(y) ++ Seq(0)
val zipped = xDigits.zipAll(yDigits, 0, 0)
val adders = zipped.scanLeft(FullAdder(0, 0, 0)) { case (acc, (i, j)) => FullAdder(acc.carry(), i, j)}.tail
fromDigits(adders.map(_.sum()))
}
val x = 145678
val y = 7865
val res = longAddition(x, y)
println("res is " + res + ", res equals x + y is " + (x + y == res))
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