Arbitrary.scala

/*-------------------------------------------------------------------------*\
**  ScalaCheck                                                             **
**  Copyright (c) 2007-2011 Rickard Nilsson. All rights reserved.          **
**  http://www.scalacheck.org                                              **
**                                                                         **
**  This software is released under the terms of the Revised BSD License.  **
**  There is NO WARRANTY. See the file LICENSE for the full text.          **
\*------------------------------------------------------------------------ */

package org.scalacheck

import util.{FreqMap,Buildable}

sealed abstract class Arbitrary[T] {
  val arbitrary: Gen[T]
}

/** Defines implicit <code>Arbitrary</code> instances for common types.
 *  <p>
 *  ScalaCheck
 *  uses implicit <code>Arbitrary</code> instances when creating properties
 *  out of functions with the <code>Prop.property</code> method, and when
 *  the <code>Arbitrary.arbitrary</code> method is used. For example, the
 *  following code requires that there exists an implicit
 *  <code>Arbitrary[MyClass]</code> instance:
 *  </p>
 *
 *  <p>
 *  <code>
 *    val myProp = Prop.forAll { myClass: MyClass =&gt;<br />
 *      ...<br />
 *    }<br />
 *
 *    val myGen = Arbitrary.arbitrary[MyClass]
 *  </code>
 *  </p>
 *
 *  <p>
 *  The required implicit definition could look like this:
 *  </p>
 *
 *  <p>
 *  <code>
 *    implicit val arbMyClass: Arbitrary[MyClass] = Arbitrary(...)
 *  </code>
 *  </p>
 *
 *  <p>
 *  The factory method <code>Arbitrary(...)</code> takes a generator of type
 *  <code>Gen[T]</code> and returns an instance of <code>Arbitrary[T]</code>.
 *  </p>
 *
 *  <p>
 *  The <code>Arbitrary</code> module defines implicit <code>Arbitrary</code>
 *  instances for common types, for convenient use in your properties and
 *  generators.
 *  </p>
 */
object Arbitrary {

  import Gen.{value, choose, sized, listOf, listOf1,
    frequency, oneOf, containerOf, resize}
  import util.StdRand
  import scala.collection.{immutable, mutable}
  import java.util.Date

  /** Creates an Arbitrary instance */
  def apply[T](g: => Gen[T]): Arbitrary[T] = new Arbitrary[T] {
    lazy val arbitrary = g
  }

  /** Returns an arbitrary generator for the type T. */
  def arbitrary[T](implicit a: Arbitrary[T]): Gen[T] = a.arbitrary

  /**** Arbitrary instances for each AnyVal ****/
  
  /** Arbitrary AnyVal */
  implicit lazy val arbAnyVal: Arbitrary[AnyVal] = Arbitrary(oneOf(
    arbitrary[Unit], arbitrary[Boolean], arbitrary[Char], arbitrary[Byte],
    arbitrary[Short], arbitrary[Int], arbitrary[Long], arbitrary[Float],
    arbitrary[Double]
  ))
 
  /** Arbitrary instance of Boolean */
  implicit lazy val arbBool: Arbitrary[Boolean] =
    Arbitrary(oneOf(true, false))

  /** Arbitrary instance of Int */
  implicit lazy val arbInt: Arbitrary[Int] = Arbitrary(
    Gen.chooseNum(Int.MinValue, Int.MaxValue)
  )

  /** Arbitrary instance of Long */
  implicit lazy val arbLong: Arbitrary[Long] = Arbitrary(
    Gen.chooseNum(Long.MinValue / 2, Long.MaxValue / 2)
  )

  /** Arbitrary instance of Float */
  implicit lazy val arbFloat: Arbitrary[Float] = Arbitrary(
    Gen.chooseNum(
      Float.MinValue, Float.MaxValue
      // I find that including these by default is a little TOO testy.
      // Float.Epsilon, Float.NaN, Float.PositiveInfinity, Float.NegativeInfinity
    )
  )

  /** Arbitrary instance of Double */
  implicit lazy val arbDouble: Arbitrary[Double] = Arbitrary(
    Gen.chooseNum(
      Double.MinValue / 2, Double.MaxValue / 2
      // As above.  Perhaps behind some option?
      // Double.Epsilon, Double.NaN, Double.PositiveInfinity, Double.NegativeInfinity
    )
  )

  /** Arbitrary instance of Char */
  implicit lazy val arbChar: Arbitrary[Char] = Arbitrary(
    Gen.frequency(
      (0xD800-Char.MinValue, Gen.choose(Char.MinValue,0xD800-1)),
      (Char.MaxValue-0xDFFF, Gen.choose(0xDFFF+1,Char.MaxValue))
    )
  )

  /** Arbitrary instance of Byte */
  implicit lazy val arbByte: Arbitrary[Byte] = Arbitrary(
    Gen.chooseNum(Byte.MinValue, Byte.MaxValue)
  )

  /** Arbitrary instance of Short */
  implicit lazy val arbShort: Arbitrary[Short] = Arbitrary(
    Gen.chooseNum(Short.MinValue, Short.MaxValue)
  )
  
  /** Absolutely, totally, 100% arbitrarily chosen Unit. */
  implicit lazy val arbUnit: Arbitrary[Unit] = Arbitrary(value(()))
  
  /**** Arbitrary instances of other common types ****/

  /** Arbitrary instance of String */
  implicit lazy val arbString: Arbitrary[String] =
    Arbitrary(arbitrary[List[Char]] map (_.mkString))
  
  /** Arbitrary instance of Date */
  implicit lazy val arbDate: Arbitrary[Date] = Arbitrary(for {
    l <- arbitrary[Long]
    d = new Date
  } yield new Date(d.getTime + l))

  /** Arbitrary instance of Throwable */
  implicit lazy val arbThrowable: Arbitrary[Throwable] =
    Arbitrary(value(new Exception))

  /** Arbitrary BigInt */
  implicit lazy val arbBigInt: Arbitrary[BigInt] = {
    def chooseBigInt: Gen[BigInt] = sized((s: Int) => choose(-s, s)) map (x => BigInt(x))
    def chooseReallyBigInt = chooseBigInt.combine(choose(32, 128))((x, y) => Some(x.get << y.get))

    Arbitrary(
      frequency(
        (5, chooseBigInt),
        (10, chooseReallyBigInt),
        (1, BigInt(0)),
        (1, BigInt(1)),
        (1, BigInt(-1)),
        (1, BigInt(Int.MaxValue) + 1),
        (1, BigInt(Int.MinValue) - 1),
        (1, BigInt(Long.MaxValue)),
        (1, BigInt(Long.MinValue)),
        (1, BigInt(Long.MaxValue) + 1),
        (1, BigInt(Long.MinValue) - 1)
      )
    )
  }
  
  /** Arbitrary BigDecimal */
  implicit lazy val arbBigDecimal: Arbitrary[BigDecimal] = {
    import java.math.MathContext._
    val mcGen = oneOf(UNLIMITED, DECIMAL32, DECIMAL64, DECIMAL128)
    val bdGen = for {
      x <- arbBigInt.arbitrary
      mc <- mcGen
      limit <- value(if(mc == UNLIMITED) 0 else math.max(x.abs.toString.length - mc.getPrecision, 0))
      scale <- Gen.chooseNum(Int.MinValue + limit , Int.MaxValue)
    } yield BigDecimal(x, scale, mc)
    Arbitrary(bdGen)
  }
  
  /** Arbitrary java.lang.Number */
  implicit lazy val arbNumber: Arbitrary[Number] = {
    val gen = Gen.oneOf(
      arbitrary[Byte], arbitrary[Short], arbitrary[Int], arbitrary[Long], 
      arbitrary[Float], arbitrary[Double]
    )
    Arbitrary(gen map (_.asInstanceOf[Number]))
    // XXX TODO - restore BigInt and BigDecimal
    // Arbitrary(oneOf(arbBigInt.arbitrary :: (arbs map (_.arbitrary) map toNumber) : _*))    
  }

  /** Generates an arbitrary property */
  implicit lazy val arbProp: Arbitrary[Prop] = {
    import Prop._
    val undecidedOrPassed = forAll { b: Boolean =>
      b ==> true
    }
    Arbitrary(frequency(
      (4, falsified),
      (4, passed),
      (3, proved),
      (3, undecidedOrPassed),
      (2, undecided),
      (1, exception(null))
    ))
  }

  /** Arbitrary instance of test params
   *  @deprecated (in 1.10.0) Use <code>arbTestParameters</code> instead.
   */
  @deprecated("Use 'arbTestParameters' instead", "1.10.0")
  implicit lazy val arbTestParams: Arbitrary[Test.Params] =
    Arbitrary(for {
      minSuccTests <- choose(10,200)
      maxDiscTests <- choose(100,500)
      mnSize <- choose(0,500)
      sizeDiff <- choose(0,500)
      mxSize <- choose(mnSize, mnSize + sizeDiff)
      ws <- choose(1,4)
    } yield Test.Params(
      minSuccessfulTests = minSuccTests,
      maxDiscardedTests = maxDiscTests,
      minSize = mnSize,
      maxSize = mxSize,
      workers = ws
    ))

  /** Arbitrary instance of test parameters */
  implicit lazy val arbTestParameters: Arbitrary[Test.Parameters] =
    Arbitrary(for {
      _minSuccTests <- choose(10,200)
      _maxDiscardRatio <- choose(0.2f,10f)
      _minSize <- choose(0,500)
      sizeDiff <- choose(0,500)
      _maxSize <- choose(_minSize, _minSize + sizeDiff)
      _workers <- choose(1,4)
    } yield new Test.Parameters.Default {
      override val minSuccessfulTests = _minSuccTests
      override val maxDiscardRatio = _maxDiscardRatio
      override val minSize = _minSize
      override val maxSize = _maxSize
      override val workers = _workers
    })

  /** Arbitrary instance of gen params */
  implicit lazy val arbGenParams: Arbitrary[Gen.Params] =
    Arbitrary(for {
      size <- arbitrary[Int] suchThat (_ >= 0)
    } yield Gen.Params(size, StdRand))

  /** Arbitrary instance of prop params */
  implicit lazy val arbPropParams: Arbitrary[Prop.Params] =
    Arbitrary(for {
      genPrms <- arbitrary[Gen.Params]
    } yield Prop.Params(genPrms, FreqMap.empty[immutable.Set[Any]]))


  // Higher-order types //

  /** Arbitrary instance of Gen */
  implicit def arbGen[T](implicit a: Arbitrary[T]): Arbitrary[Gen[T]] =
    Arbitrary(frequency(
      (5, arbitrary[T] map (value(_))),
      (1, Gen.fail)
    ))

  /** Arbitrary instance of option type */
  implicit def arbOption[T](implicit a: Arbitrary[T]): Arbitrary[Option[T]] =
    Arbitrary(sized(n => if(n == 0) value(None) else resize(n - 1, arbitrary[T]).map(Some(_))))

  implicit def arbEither[T, U](implicit at: Arbitrary[T], au: Arbitrary[U]): Arbitrary[Either[T, U]] =
    Arbitrary(oneOf(arbitrary[T].map(Left(_)), arbitrary[U].map(Right(_))))

  /** Arbitrary instance of immutable map */
  implicit def arbImmutableMap[T,U](implicit at: Arbitrary[T], au: Arbitrary[U]
  ): Arbitrary[immutable.Map[T,U]] = Arbitrary(
    for(seq <- arbitrary[Stream[(T,U)]]) yield immutable.Map(seq: _*)
  )

  /** Arbitrary instance of mutable map */
  implicit def arbMutableMap[T,U](implicit at: Arbitrary[T], au: Arbitrary[U]
  ): Arbitrary[mutable.Map[T,U]] = Arbitrary(
    for(seq <- arbitrary[Stream[(T,U)]]) yield mutable.Map(seq: _*)
  )

  /** Arbitrary instance of any buildable container (such as lists, arrays,
   *  streams, etc). The maximum size of the container depends on the size
   *  generation parameter. */
  implicit def arbContainer[C[_],T](implicit a: Arbitrary[T], b: Buildable[T,C]
  ): Arbitrary[C[T]] = Arbitrary(containerOf[C,T](arbitrary[T]))

  /** Arbitrary instance of any array. */
  implicit def arbArray[T](implicit a: Arbitrary[T], c: ClassManifest[T]
  ): Arbitrary[Array[T]] = Arbitrary(containerOf[Array,T](arbitrary[T]))


  // Functions //

  /** Arbitrary instance of Function1 */
  implicit def arbFunction1[T1,R](implicit a: Arbitrary[R]
  ): Arbitrary[T1 => R] = Arbitrary(
    for(r <- arbitrary[R]) yield (t1: T1) => r
  )

  /** Arbitrary instance of Function2 */
  implicit def arbFunction2[T1,T2,R](implicit a: Arbitrary[R]
  ): Arbitrary[(T1,T2) => R] = Arbitrary(
    for(r <- arbitrary[R]) yield (t1: T1, t2: T2) => r
  )

  /** Arbitrary instance of Function3 */
  implicit def arbFunction3[T1,T2,T3,R](implicit a: Arbitrary[R]
  ): Arbitrary[(T1,T2,T3) => R] = Arbitrary(
    for(r <- arbitrary[R]) yield (t1: T1, t2: T2, t3: T3) => r
  )

  /** Arbitrary instance of Function4 */
  implicit def arbFunction4[T1,T2,T3,T4,R](implicit a: Arbitrary[R]
  ): Arbitrary[(T1,T2,T3,T4) => R] = Arbitrary(
    for(r <- arbitrary[R]) yield (t1: T1, t2: T2, t3: T3, t4: T4) => r
  )

  /** Arbitrary instance of Function5 */
  implicit def arbFunction5[T1,T2,T3,T4,T5,R](implicit a: Arbitrary[R]
  ): Arbitrary[(T1,T2,T3,T4,T5) => R] = Arbitrary(
    for(r <- arbitrary[R]) yield (t1: T1, t2: T2, t3: T3, t4: T4, t5: T5) => r
  )


  // Tuples //

  /** Arbitrary instance of 2-tuple */
  implicit def arbTuple2[T1,T2](implicit
    a1: Arbitrary[T1], a2: Arbitrary[T2]
  ): Arbitrary[(T1,T2)] =
    Arbitrary(for {
      t1 <- arbitrary[T1]
      t2 <- arbitrary[T2]
    } yield (t1,t2))

  /** Arbitrary instance of 3-tuple */
  implicit def arbTuple3[T1,T2,T3](implicit
    a1: Arbitrary[T1], a2: Arbitrary[T2], a3: Arbitrary[T3]
  ): Arbitrary[(T1,T2,T3)] =
    Arbitrary(for {
      t1 <- arbitrary[T1]
      t2 <- arbitrary[T2]
      t3 <- arbitrary[T3]
    } yield (t1,t2,t3))

  /** Arbitrary instance of 4-tuple */
  implicit def arbTuple4[T1,T2,T3,T4](implicit
    a1: Arbitrary[T1], a2: Arbitrary[T2], a3: Arbitrary[T3], a4: Arbitrary[T4]
  ): Arbitrary[(T1,T2,T3,T4)] =
    Arbitrary(for {
      t1 <- arbitrary[T1]
      t2 <- arbitrary[T2]
      t3 <- arbitrary[T3]
      t4 <- arbitrary[T4]
    } yield (t1,t2,t3,t4))

  /** Arbitrary instance of 5-tuple */
  implicit def arbTuple5[T1,T2,T3,T4,T5](implicit
    a1: Arbitrary[T1], a2: Arbitrary[T2], a3: Arbitrary[T3], a4: Arbitrary[T4],
    a5: Arbitrary[T5]
  ): Arbitrary[(T1,T2,T3,T4,T5)] =
    Arbitrary(for {
      t1 <- arbitrary[T1]
      t2 <- arbitrary[T2]
      t3 <- arbitrary[T3]
      t4 <- arbitrary[T4]
      t5 <- arbitrary[T5]
    } yield (t1,t2,t3,t4,t5))

  /** Arbitrary instance of 6-tuple */
  implicit def arbTuple6[T1,T2,T3,T4,T5,T6](implicit
    a1: Arbitrary[T1], a2: Arbitrary[T2], a3: Arbitrary[T3], a4: Arbitrary[T4],
    a5: Arbitrary[T5], a6: Arbitrary[T6]
  ): Arbitrary[(T1,T2,T3,T4,T5,T6)] =
    Arbitrary(for {
      t1 <- arbitrary[T1]
      t2 <- arbitrary[T2]
      t3 <- arbitrary[T3]
      t4 <- arbitrary[T4]
      t5 <- arbitrary[T5]
      t6 <- arbitrary[T6]
    } yield (t1,t2,t3,t4,t5,t6))

  /** Arbitrary instance of 7-tuple */
  implicit def arbTuple7[T1,T2,T3,T4,T5,T6,T7](implicit
    a1: Arbitrary[T1], a2: Arbitrary[T2], a3: Arbitrary[T3], a4: Arbitrary[T4],
    a5: Arbitrary[T5], a6: Arbitrary[T6], a7: Arbitrary[T7]
  ): Arbitrary[(T1,T2,T3,T4,T5,T6,T7)] =
    Arbitrary(for {
      t1 <- arbitrary[T1]
      t2 <- arbitrary[T2]
      t3 <- arbitrary[T3]
      t4 <- arbitrary[T4]
      t5 <- arbitrary[T5]
      t6 <- arbitrary[T6]
      t7 <- arbitrary[T7]
    } yield (t1,t2,t3,t4,t5,t6,t7))

  /** Arbitrary instance of 8-tuple */
  implicit def arbTuple8[T1,T2,T3,T4,T5,T6,T7,T8](implicit
    a1: Arbitrary[T1], a2: Arbitrary[T2], a3: Arbitrary[T3], a4: Arbitrary[T4],
    a5: Arbitrary[T5], a6: Arbitrary[T6], a7: Arbitrary[T7], a8: Arbitrary[T8]
  ): Arbitrary[(T1,T2,T3,T4,T5,T6,T7,T8)] =
    Arbitrary(for {
      t1 <- arbitrary[T1]
      t2 <- arbitrary[T2]
      t3 <- arbitrary[T3]
      t4 <- arbitrary[T4]
      t5 <- arbitrary[T5]
      t6 <- arbitrary[T6]
      t7 <- arbitrary[T7]
      t8 <- arbitrary[T8]
    } yield (t1,t2,t3,t4,t5,t6,t7,t8))

  /** Arbitrary instance of 9-tuple */
  implicit def arbTuple9[T1,T2,T3,T4,T5,T6,T7,T8,T9](implicit
    a1: Arbitrary[T1], a2: Arbitrary[T2], a3: Arbitrary[T3], a4: Arbitrary[T4],
    a5: Arbitrary[T5], a6: Arbitrary[T6], a7: Arbitrary[T7], a8: Arbitrary[T8],
    a9: Arbitrary[T9]
  ): Arbitrary[(T1,T2,T3,T4,T5,T6,T7,T8,T9)] =
    Arbitrary(for {
      t1 <- arbitrary[T1]
      t2 <- arbitrary[T2]
      t3 <- arbitrary[T3]
      t4 <- arbitrary[T4]
      t5 <- arbitrary[T5]
      t6 <- arbitrary[T6]
      t7 <- arbitrary[T7]
      t8 <- arbitrary[T8]
      t9 <- arbitrary[T9]
    } yield (t1,t2,t3,t4,t5,t6,t7,t8,t9))

}