Scala example source code file (genprod.scala)

This example Scala source code file (genprod.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

a, abstractfunction, arity, double, function, group, int, product, r, tuple

The genprod.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

import scala.language.postfixOps

/** This program generates the ProductN, TupleN, FunctionN,
 *  and AbstractFunctionN, where 0 <= N <= MAX_ARITY.
 *
 *    Usage: scala genprod <directory>
 *      where the argument is the desired output directory
 *
 *  @author  Burak Emir, Stephane Micheloud, Geoffrey Washburn, Paul Phillips
 *  @version 1.1
 */
object genprod extends App {
  val MAX_ARITY = 22
  def arities = (1 to MAX_ARITY).toList

  class Group(val name: String) {
    def className(i: Int) = name + i
    def fileName(i: Int) = className(i) + ".scala"
  }

  def productFiles  = arities map Product.make
  def tupleFiles    = arities map Tuple.make
  def functionFiles = (0 :: arities) map Function.make
  def absFunctionFiles = (0 :: arities) map AbstractFunction.make
  def allfiles      = productFiles ::: tupleFiles ::: functionFiles ::: absFunctionFiles

  trait Arity extends Group {
    def i: Int    // arity

    def typeArgsString(xs: Seq[String]) = xs.mkString("[", ", ", "]")

    def to              = (1 to i).toList
    def s               = if (i == 1) "" else "s"
    def className       = name + i
    def classAnnotation = ""
    def fileName        = className + ".scala"
    def targs           = to map ("T" + _)
    def vdefs           = to map ("v" + _)
    def xdefs           = to map ("x" + _)
    def mdefs           = to map ("_" + _)
    def invariantArgs   = typeArgsString(targs)
    def covariantArgs   = typeArgsString(targs map (covariantSpecs + "+" + _))
    def covariantSpecs  = ""
    def contravariantSpecs = ""
    def contraCoArgs    = typeArgsString((targs map (contravariantSpecs + "-" + _)) ::: List(covariantSpecs + "+R"))
    def constructorArgs = (targs).map( _.toLowerCase ) mkString ", "
    def fields          = (mdefs, targs).zipped.map(_ + ": " + _) mkString ", "
    def funArgs         = (vdefs, targs).zipped.map(_ + ": " + _) mkString ", "

    def genprodString       = " See scala.Function0 for timestamp."
    def moreMethods         = ""
    def packageDef          = "scala"
    def imports             = ""

    def header = """
/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */
// GENERATED CODE: DO NOT EDIT.%s

package %s
%s
""".trim.format(genprodString, packageDef, imports)
  }

  if (args.length != 1) {
    println("please give path of output directory")
    sys.exit(-1)
  }
  val out = args(0)
  def writeFile(node: scala.xml.Node) {
    import scala.tools.nsc.io._
    val f = Path(out) / node.attributes("name").toString
    f.parent.createDirectory(force = true)
    f.toFile writeAll node.text
  }

  allfiles foreach writeFile
}
import genprod._


/* zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
                             F U N C T I O N
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz */

object FunctionZero extends Function(0) {
  override def genprodString  = "\n// genprod generated these sources at: " + new java.util.Date()
  override def covariantSpecs = "@specialized(Specializable.Primitives) "
  override def descriptiveComment = "  " + functionNTemplate.format("javaVersion", "anonfun0",
"""
 *    val javaVersion = () => sys.props("java.version")
 *
 *    val anonfun0 = new Function0[String] {
 *      def apply(): String = sys.props("java.version")
 *    }
 *    assert(javaVersion() == anonfun0())
 * """)
  override def moreMethods = ""
}

object FunctionOne extends Function(1) {
  override def classAnnotation    = "@annotation.implicitNotFound(msg = \"No implicit view available from ${T1} => ${R}.\")\n"
  override def contravariantSpecs = "@specialized(scala.Int, scala.Long, scala.Float, scala.Double) "
  override def covariantSpecs     = "@specialized(scala.Unit, scala.Boolean, scala.Int, scala.Float, scala.Long, scala.Double) "

  override def descriptiveComment = "  " + functionNTemplate.format("succ", "anonfun1",
"""
 *    val succ = (x: Int) => x + 1
 *    val anonfun1 = new Function1[Int, Int] {
 *      def apply(x: Int): Int = x + 1
 *    }
 *    assert(succ(0) == anonfun1(0))
 * """)

  override def moreMethods = """
  /** Composes two instances of Function1 in a new Function1, with this function applied last.
   *
   *  @tparam   A   the type to which function `g` can be applied
   *  @param    g   a function A => T1
   *  @return       a new function `f` such that `f(x) == apply(g(x))`
   */
  @annotation.unspecialized def compose[A](g: A => T1): A => R = { x => apply(g(x)) }

  /** Composes two instances of Function1 in a new Function1, with this function applied first.
   *
   *  @tparam   A   the result type of function `g`
   *  @param    g   a function R => A
   *  @return       a new function `f` such that `f(x) == g(apply(x))`
   */
  @annotation.unspecialized def andThen[A](g: R => A): T1 => A = { x => g(apply(x)) }
"""
}

object FunctionTwo extends Function(2) {
  override def contravariantSpecs = "@specialized(scala.Int, scala.Long, scala.Double) "
  override def covariantSpecs = "@specialized(scala.Unit, scala.Boolean, scala.Int, scala.Float, scala.Long, scala.Double) "

  override def descriptiveComment = "  " + functionNTemplate.format("max", "anonfun2",
"""
 *    val max = (x: Int, y: Int) => if (x < y) y else x
 *
 *    val anonfun2 = new Function2[Int, Int, Int] {
 *      def apply(x: Int, y: Int): Int = if (x < y) y else x
 *    }
 *    assert(max(0, 1) == anonfun2(0, 1))
 * """)
}

object Function {
  def make(i: Int) = apply(i)()
  def apply(i: Int) = i match {
    case 0    => FunctionZero
    case 1    => FunctionOne
    case 2    => FunctionTwo
    case _    => new Function(i)
  }
}

class Function(val i: Int) extends Group("Function") with Arity {
  def descriptiveComment  = ""
  def functionNTemplate =
"""
 *  In the following example, the definition of %s is a
 *  shorthand for the anonymous class definition %s:
 *
 *  {{{
 *  object Main extends App {%s}
 *  }}}
 *
 *  Note that `Function1` does not define a total function, as might
 *  be suggested by the existence of [[scala.PartialFunction]]. The only
 *  distinction between `Function1` and `PartialFunction` is that the
 *  latter can specify inputs which it will not handle.
"""

  def toStr() = "\"" + ("<function%d>" format i) + "\""
  def apply() = {
<file name={fileName}>{header}

/** A function of {i} parameter{s}.
 *{descriptiveComment}
 */
{classAnnotation}trait {className}{contraCoArgs} extends AnyRef {{ self =>
  /** Apply the body of this function to the argument{s}.
   *  @return   the result of function application.
   */
  def apply({funArgs}): R
{moreMethods}
  override def toString() = {toStr}
}}
</file>
}

  private def commaXs = xdefs.mkString("(", ", ", ")")

  // (x1: T1) => (x2: T2) => (x3: T3) => (x4: T4) => apply(x1,x2,x3,x4)
  def shortCurry = {
    val body = "apply" + commaXs
    (xdefs, targs).zipped.map("(%s: %s) => ".format(_, _)).mkString("", "", body)
  }

  // (x1: T1) => ((x2: T2, x3: T3, x4: T4, x5: T5, x6: T6, x7: T7) => self.apply(x1,x2,x3,x4,x5,x6,x7)).curried
  def longCurry = ((xdefs, targs).zipped.map(_ + ": " + _) drop 1).mkString(
    "(x1: T1) => ((",
    ", ",
    ") => self.apply%s).curried".format(commaXs)
  )

  // f(x1,x2,x3,x4,x5,x6)  == (f.curried)(x1)(x2)(x3)(x4)(x5)(x6)
  def curryComment = {
"""  /** Creates a curried version of this function.
   *
   *  @return   a function `f` such that `f%s == apply%s`
   */""".format(xdefs map ("(" + _ + ")") mkString, commaXs)
  }

  def tupleMethod = {
    def comment =
"""  /** Creates a tupled version of this function: instead of %d arguments,
   *  it accepts a single [[scala.Tuple%d]] argument.
   *
   *  @return   a function `f` such that `f(%s) == f(Tuple%d%s) == apply%s`
   */
""".format(i, i, commaXs, i, commaXs, commaXs)
    def body = "case Tuple%d%s => apply%s".format(i, commaXs, commaXs)

    comment + "\n  @annotation.unspecialized def tupled: Tuple%d%s => R = {\n    %s\n  }".format(i, invariantArgs, body)
  }

  def curryMethod = {
    val body = if (i < 5) shortCurry else longCurry

    curryComment +
    "\n  @annotation.unspecialized def curried: %s => R = {\n    %s\n  }\n".format(
      targs mkString " => ", body
    )
  }

  override def moreMethods = curryMethod + tupleMethod
} // object Function


/* zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
                                     T U P L E
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz */

object Tuple {
  val zipImports = ""

  def make(i: Int) = apply(i)()
  def apply(i: Int) = i match {
    case 1  => TupleOne
    case 2  => TupleTwo
    case 3  => TupleThree
    case _  => new Tuple(i)
  }
}

object TupleOne extends Tuple(1)
{
  override def covariantSpecs = "@specialized(Int, Long, Double) "
}

object TupleTwo extends Tuple(2)
{
  override def imports = Tuple.zipImports
  override def covariantSpecs = "@specialized(Int, Long, Double, Char, Boolean/*, AnyRef*/) "
  override def moreMethods = """
  /** Swaps the elements of this `Tuple`.
   * @return a new Tuple where the first element is the second element of this Tuple and the
   * second element is the first element of this Tuple.
   */
  def swap: Tuple2[T2,T1] = Tuple2(_2, _1)
"""
}

object TupleThree extends Tuple(3) {
  override def imports = Tuple.zipImports
}

class Tuple(val i: Int) extends Group("Tuple") with Arity {
  private def idiomatic =
    if (i < 2) ""
    else " Note that it is more idiomatic to create a %s via `(%s)`".format(className, constructorArgs)

  private def params = (
    1 to i map (x => " *  @param  _%d   Element %d of this Tuple%d".format(x, x, i))
  ) mkString "\n"

  // prettifies it a little if it's overlong
  def mkToString() = {
  def str(xs: List[String]) = xs.mkString(""" + "," + """)
    if (i <= MAX_ARITY / 2) str(mdefs)
    else {
      val s1 = str(mdefs take (i / 2))
      val s2 = str(mdefs drop (i / 2))
      s1 + " +\n    \",\" + " + s2
    }
  }

  def apply() = {
<file name={fileName}>{header}

/** A tuple of {i} elements; the canonical representation of a [[scala.{Product.className(i)}]].
 *
 *  @constructor  Create a new tuple with {i} elements.{idiomatic}
{params}
 */
@deprecatedInheritance("Tuples will be made final in a future version.", "2.11.0")
case class {className}{covariantArgs}({fields})
  extends {Product.className(i)}{invariantArgs}
{{
  override def toString() = "(" + {mkToString} + ")"
  {moreMethods}
}}
</file>}
} // object Tuple


/* zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
                                  P R O D U C T
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz */

object Product extends Group("Product")
{
  def make(i: Int) = apply(i)()
  def apply(i: Int) = i match {
    case 1  => ProductOne
    case 2  => ProductTwo
    case _ => new Product(i)
  }
}

object ProductOne extends Product(1)
{
  override def covariantSpecs = "@specialized(Int, Long, Double) "
}

object ProductTwo extends Product(2)
{
  override def covariantSpecs = "@specialized(Int, Long, Double) "
}

class Product(val i: Int) extends Group("Product") with Arity {
  val productElementComment = """
  /** Returns the n-th projection of this product if 0 < n <= productArity,
   *  otherwise throws an `IndexOutOfBoundsException`.
   *
   *  @param n number of the projection to be returned
   *  @return  same as `._(n+1)`, for example `productElement(0)` is the same as `._1`.
   *  @throws  IndexOutOfBoundsException
   */
"""

  def cases = {
    val xs = for ((x, i) <- mdefs.zipWithIndex) yield "case %d => %s".format(i, x)
    val default = "case _ => throw new IndexOutOfBoundsException(n.toString())"
    "\n" + ((xs ::: List(default)) map ("    " + _ + "\n") mkString)
  }
  def proj = {
    (mdefs,targs).zipped.map( (_,_) ).zipWithIndex.map { case ((method,typeName),index) =>
      """|  /** A projection of element %d of this Product.
         |   *  @return   A projection of element %d.
         |   */
         |  def %s: %s
         |""".stripMargin.format(index + 1, index + 1, method, typeName)
    } mkString
  }

  def apply() = {
<file name={fileName}>{header}
object {className} {{
  def unapply{invariantArgs}(x: {className}{invariantArgs}): Option[{className}{invariantArgs}] =
    Some(x)
}}

/** {className} is a cartesian product of {i} component{s}.
 *  @since 2.3
 */
trait {className}{covariantArgs} extends Any with Product {{
  /** The arity of this product.
   *  @return {i}
   */
  override def productArity = {i}

  {productElementComment}
  @throws(classOf[IndexOutOfBoundsException])
  override def productElement(n: Int) = n match {{ {cases} }}

{proj}
{moreMethods}
}}
</file>}

}

/** Abstract functions **/

object AbstractFunctionZero extends AbstractFunction(0) {
  override def covariantSpecs = FunctionZero.covariantSpecs
}

object AbstractFunctionOne extends AbstractFunction(1) {
  override def covariantSpecs = FunctionOne.covariantSpecs
  override def contravariantSpecs = FunctionOne.contravariantSpecs
}

object AbstractFunctionTwo extends AbstractFunction(2) {
  override def covariantSpecs = FunctionTwo.covariantSpecs
  override def contravariantSpecs = FunctionTwo.contravariantSpecs
}

class AbstractFunction(val i: Int) extends Group("AbstractFunction") with Arity
{
  override def packageDef = "scala.runtime"

  val superTypeArgs = typeArgsString(targs ::: List("R"))

  def apply() = {
<file name={"runtime/" + fileName}>{header}
abstract class {className}{contraCoArgs} extends Function{i}{superTypeArgs} {{
{moreMethods}
}}
</file>}

}
object AbstractFunction
{
  def make(i: Int) = apply(i)()
  def apply(i: Int) = i match {
    case 0    => AbstractFunctionZero
    case 1    => AbstractFunctionOne
    case 2    => AbstractFunctionTwo
    case _    => new AbstractFunction(i)
  }
}