GettingStarted.scala

//
// 第２章の演習問題を自分で問いてみる
//


object MyModule{
	def fib(n: Int): Int = n match {
		case 0 => 0
		case 1 => 1
		case n => fib(n-1) + fib(n-2)
	}

	def factorial(n: Int): Int = {
		@annotation.tailrec
		def go(n: Int, acc: Int): Int =
			if (n <= 0) acc
			else go(n-1, n*acc)
		go(n, 1)
	}

	def sum(n: Int): Int = {
		@annotation.tailrec
		def go(n: Int, acc: Int): Int =
			if (n <= 0) acc
			else go(n-1, n+acc)
		go(n, 0)
	}
/*
	private def formatSum(x: Int) = {
		val msg = "The total sum value of %d is %d"
		msg.format(x, sum(x))
	}
*/

	def abs(n: Int): Int =
		if (n < 0) -n
		else n
/*
	private def formatAbs(x: Int) = {
		val msg = "The absolute value of %d is %d"
		msg.format(x, abs(x))
	}
*/
	def formatResult(name: String, n: Int, f: Int => Int) = {
		val msg = "The %s of %d is %d."
		msg.format(name, n, f(n))
	}

	def main(args: Array[String]): Unit =
		//println(formatAbs(-321))
		//println(formatSum(10))
		println(formatResult("total sum", 10, sum))
		println(formatResult("factorial", 5, factorial))
		println(formatResult("Fibonacci", 5, fib))

}