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jeffreyolchovy/RecursiveStreams.scala

Created August 30, 2012 15:15
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Revisions

  1. jeffreyolchovy revised this gist Aug 30, 2012. 1 changed file with 9 additions and 3 deletions.
    12 changes: 9 additions & 3 deletions RecursiveStreams.scala
    View file
    Original file line number Diff line number Diff line change
    @@ -1,4 +1,4 @@
    import scala.math.BigInt
    import scala.math.{BigInt, BigDecimal}

    object RecursiveStreams
    {
    @@ -11,6 +11,11 @@ object RecursiveStreams
    // factorials
    lazy val fac: Stream[BigInt] = Stream.cons(BigInt(1), fac.zip(N).map(a => a._1 * a._2))

    // pi / 4
    lazy val piOver4: Stream[Double] = Stream.cons(1d, N.map(a => (1 - (a.toDouble % 2) * 2) / (2 * a.toDouble + 1)))

    def estimatePi(n: Int): Double = piOver4.take(n).sum * 4

    def main(args: Array[String]) {
    assert(N(0) == 1)
    assert(fib(0) == 0)
    @@ -22,6 +27,7 @@ object RecursiveStreams
    println("First 10 natural numbers: %s".format(N.take(10).mkString(" ")))
    println("First 10 fibonacci numbers: %s".format(fib.take(10).mkString(" ")))
    println("First 10 factorials: %s".format(fac.take(10).mkString(" ")))
    }
    }

    println("Pi estimate: %s".format(estimatePi(5000)))
    }
    }
  2. jeffreyolchovy created this gist Aug 30, 2012.
    27 changes: 27 additions & 0 deletions RecursiveStreams.scala
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,27 @@
    import scala.math.BigInt

    object RecursiveStreams
    {
    // natural numbers
    lazy val N: Stream[BigInt] = Stream.cons(BigInt(1), N.map(_ + 1))

    // fibonacci series
    lazy val fib: Stream[BigInt] = Stream.cons(BigInt(0), Stream.cons(BigInt(1), fib.zip(fib.tail).map(a => a._1 + a._2)))

    // factorials
    lazy val fac: Stream[BigInt] = Stream.cons(BigInt(1), fac.zip(N).map(a => a._1 * a._2))

    def main(args: Array[String]) {
    assert(N(0) == 1)
    assert(fib(0) == 0)
    assert(fac(0) == 1)

    assert(fib(5) == 5)
    assert(fac(5) == 120)

    println("First 10 natural numbers: %s".format(N.take(10).mkString(" ")))
    println("First 10 fibonacci numbers: %s".format(fib.take(10).mkString(" ")))
    println("First 10 factorials: %s".format(fac.take(10).mkString(" ")))
    }
    }