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author | Paul Phillips <paulp@improving.org> | 2012-03-30 20:54:05 -0700 |
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committer | Paul Phillips <paulp@improving.org> | 2012-03-30 20:54:05 -0700 |
commit | 03aca2c5bc293f8fd79e99b2aaac79cdc043c1da (patch) | |
tree | ea832b582e355f1a6687b286266b59b8108188c6 /src/library | |
parent | dc8b431f1c38ff805d660c44b19ee5ecc91bddb2 (diff) | |
parent | 1890a4175dc6c436b37ddc8c6b74e036b9c6328c (diff) | |
download | scala-03aca2c5bc293f8fd79e99b2aaac79cdc043c1da.tar.gz scala-03aca2c5bc293f8fd79e99b2aaac79cdc043c1da.tar.bz2 scala-03aca2c5bc293f8fd79e99b2aaac79cdc043c1da.zip |
Merge remote-tracking branch 'adriaanm/topic/partialfun' into develop
Diffstat (limited to 'src/library')
-rw-r--r-- | src/library/scala/Function.scala | 7 | ||||
-rw-r--r-- | src/library/scala/PartialFunction.scala | 134 | ||||
-rw-r--r-- | src/library/scala/runtime/AbstractPartialFunction.scala | 84 | ||||
-rw-r--r-- | src/library/scala/util/control/Exception.scala | 5 |
4 files changed, 154 insertions, 76 deletions
diff --git a/src/library/scala/Function.scala b/src/library/scala/Function.scala index 4a10b65735..9fa56a332f 100644 --- a/src/library/scala/Function.scala +++ b/src/library/scala/Function.scala @@ -29,6 +29,7 @@ object Function { /** Turns a function `A => Option[B]` into a `PartialFunction[A, B]`. * + * TODO: check if the paragraph below is still correct * '''Important note''': this transformation implies the original function * will be called 2 or more times on each logical invocation, because the * only way to supply an implementation of `isDefinedAt` is to call the @@ -39,11 +40,7 @@ object Function { * f returns `Some(_)` and undefined where `f` returns `None`. * @see [[scala.PartialFunction#lift]] */ - def unlift[T, R](f: T => Option[R]): PartialFunction[T, R] = new runtime.AbstractPartialFunction[T, R] { - def apply(x: T): R = f(x).get - def _isDefinedAt(x: T): Boolean = f(x).isDefined - override def lift: T => Option[R] = f - } + def unlift[T, R](f: T => Option[R]): PartialFunction[T, R] = PartialFunction.unlifted(f) /** Uncurrying for functions of arity 2. This transforms a unary function * returning another unary function into a function of arity 2. diff --git a/src/library/scala/PartialFunction.scala b/src/library/scala/PartialFunction.scala index 3c5d6d0d23..7154b8da34 100644 --- a/src/library/scala/PartialFunction.scala +++ b/src/library/scala/PartialFunction.scala @@ -8,6 +8,7 @@ package scala + /** A partial function of type `PartialFunction[A, B]` is a unary function * where the domain does not necessarily include all values of type `A`. * The function `isDefinedAt` allows to test dynamically if a value is in @@ -43,10 +44,11 @@ package scala * }}} * * - * @author Martin Odersky + * @author Martin Odersky, Pavel Pavlov, Adriaan Moors * @version 1.0, 16/07/2003 */ -trait PartialFunction[-A, +B] extends (A => B) { +trait PartialFunction[-A, +B] extends (A => B) { self => + import PartialFunction._ /** Checks if a value is contained in the function's domain. * @@ -55,10 +57,6 @@ trait PartialFunction[-A, +B] extends (A => B) { */ def isDefinedAt(x: A): Boolean - //protected def missingCase[A1 <: A, B1 >: B]: PartialFunction[A1, B1] = PartialFunction.empty - - protected def missingCase(x: A): B = throw new MatchError(x) - /** Composes this partial function with a fallback partial function which * gets applied where this partial function is not defined. * @@ -70,16 +68,8 @@ trait PartialFunction[-A, +B] extends (A => B) { * takes `x` to `this(x)` where `this` is defined, and to `that(x)` where it is not. */ def orElse[A1 <: A, B1 >: B](that: PartialFunction[A1, B1]) : PartialFunction[A1, B1] = - new runtime.AbstractPartialFunction[A1, B1] { - def _isDefinedAt(x: A1): Boolean = - PartialFunction.this.isDefinedAt(x) || that.isDefinedAt(x) - def apply(x: A1): B1 = - if (PartialFunction.this.isDefinedAt(x)) PartialFunction.this.apply(x) - else that.apply(x) - } - - def orElseFast[A1 <: A, B1 >: B](that: PartialFunction[A1, B1]) : PartialFunction[A1, B1] = - orElse(that) + new OrElse[A1, B1] (this, that) + //TODO: why not overload it with orElse(that: F1): F1? /** Composes this partial function with a transformation function that * gets applied to results of this partial function. @@ -88,9 +78,9 @@ trait PartialFunction[-A, +B] extends (A => B) { * @return a partial function with the same domain as this partial function, which maps * arguments `x` to `k(this(x))`. */ - override def andThen[C](k: B => C) : PartialFunction[A, C] = new runtime.AbstractPartialFunction[A, C] { - def _isDefinedAt(x: A): Boolean = PartialFunction.this.isDefinedAt(x) - def apply(x: A): C = k(PartialFunction.this.apply(x)) + override def andThen[C](k: B => C) : PartialFunction[A, C] = new PartialFunction[A, C] { + def isDefinedAt(x: A): Boolean = self isDefinedAt x + def apply(x: A): C = k(self(x)) } /** Turns this partial function into an plain function returning an `Option` result. @@ -98,9 +88,30 @@ trait PartialFunction[-A, +B] extends (A => B) { * @return a function that takes an argument `x` to `Some(this(x))` if `this` * is defined for `x`, and to `None` otherwise. */ - def lift: A => Option[B] = new (A => Option[B]) { - def apply(x: A): Option[B] = if (isDefinedAt(x)) Some(PartialFunction.this.apply(x)) else None - } + def lift: A => Option[B] = new Lifted(this) + + /** + * TODO: comment + * @since 2.10 + */ + def applyOrElse[A1 <: A, B1 >: B](x: A1, default: A1 => B1): B1 = + if (isDefinedAt(x)) apply(x) else default(x) + + /** + * TODO: comment + * @since 2.10 + */ + def run[U](x: A)(action: B => U): Boolean = + applyOrElse(x, fallbackToken) match { + case FallbackToken => false + case z => action(z); true + } + + /** + * TODO: comment + * @since 2.10 + */ + def runWith[U](action: B => U): A => Boolean = { x => run(x)(action) } } /** A few handy operations which leverage the extra bit of information @@ -119,14 +130,73 @@ trait PartialFunction[-A, +B] extends (A => B) { * @since 2.8 */ object PartialFunction { - private[this] final val empty_pf: PartialFunction[Any, Nothing] = new runtime.AbstractPartialFunction[Any, Nothing] { - def _isDefinedAt(x: Any) = false - override def isDefinedAt(x: Any) = false - def apply(x: Any): Nothing = throw new MatchError(x) - override def orElse[A1, B1](that: PartialFunction[A1, B1]): PartialFunction[A1, B1] = that - override def orElseFast[A1, B1](that: PartialFunction[A1, B1]): PartialFunction[A1, B1] = that - override def lift = (x: Any) => None + /** Composite function produced by `PartialFunction#orElse` method + */ + private final class OrElse[-A, +B] (f1: PartialFunction[A, B], f2: PartialFunction[A, B]) extends PartialFunction[A, B] { + def isDefinedAt(x: A) = f1.isDefinedAt(x) || f2.isDefinedAt(x) + + def apply(x: A): B = f1.applyOrElse(x, f2) + + override def applyOrElse[A1 <: A, B1 >: B](x: A1, default: A1 => B1): B1 = + f1.applyOrElse(x, fallbackToken) match { + case FallbackToken => f2.applyOrElse(x, default) + case z => z + } + + override def orElse[A1 <: A, B1 >: B](that: PartialFunction[A1, B1]) = + new OrElse[A1, B1] (f1, f2 orElse that) + + override def andThen[C](k: B => C) = + new OrElse[A, C] (f1 andThen k, f2 andThen k) } + + private[scala] lazy val FallbackToken: PartialFunction[Any, PartialFunction[Any, Nothing]] = { case _ => FallbackToken.asInstanceOf[PartialFunction[Any, Nothing]] } + private[scala] final def fallbackToken[B] = FallbackToken.asInstanceOf[PartialFunction[Any, B]] + //TODO: check generated code for PF literal here + + private[scala] final class Lifted[-A, +B] (val pf: PartialFunction[A, B]) + extends runtime.AbstractFunction1[A, Option[B]] { + + def apply(x: A): Option[B] = pf.applyOrElse(x, fallbackToken) match { + case FallbackToken => None + case z => Some(z) + } + } + + private final class Unlifted[A, B] (f: A => Option[B]) extends runtime.AbstractPartialFunction[A, B] { + def isDefinedAt(x: A): Boolean = f(x).isDefined + override def applyOrElse[A1 <: A, B1 >: B](x: A1, default: A1 => B1): B1 = + f(x) getOrElse default(x) //TODO: check generated code and inline getOrElse if needed + override def lift = f + } + + private[scala] def unlifted[A, B](f: A => Option[B]): PartialFunction[A, B] = f match { + case lf: Lifted[A, B] => lf.pf + case ff => new Unlifted(ff) + } + + /** Converts ordinary function to partial one + * @since 2.10 + */ + //TODO: check generated code for PF literal here + def apply[A, B](f: A => B): PartialFunction[A, B] = { case x => f(x) } + + private[this] final val constFalse: Any => Boolean = { _ => false} + + private[this] final val empty_pf: PartialFunction[Any, Nothing] = new PartialFunction[Any, Nothing] { + def isDefinedAt(x: Any) = false + def apply(x: Any) = throw new MatchError(x) + override def orElse[A1, B1](that: PartialFunction[A1, B1]) = that + override def andThen[C](k: Nothing => C) = this + override val lift = (x: Any) => None + override def run[U](x: Any)(action: Nothing => U) = false + override def runWith[U](action: Nothing => U) = constFalse + } + + /** + * TODO: comment + * @since 2.10 + */ def empty[A, B] : PartialFunction[A, B] = empty_pf /** Creates a Boolean test based on a value and a partial function. @@ -137,8 +207,7 @@ object PartialFunction { * @param pf the partial function * @return true, iff `x` is in the domain of `pf` and `pf(x) == true`. */ - def cond[T](x: T)(pf: PartialFunction[T, Boolean]): Boolean = - (pf isDefinedAt x) && pf(x) + def cond[T](x: T)(pf: PartialFunction[T, Boolean]): Boolean = pf.applyOrElse(x, constFalse) /** Transforms a PartialFunction[T, U] `pf` into Function1[T, Option[U]] `f` * whose result is `Some(x)` if the argument is in `pf`'s domain and `None` @@ -150,6 +219,5 @@ object PartialFunction { * @param pf the PartialFunction[T, U] * @return `Some(pf(x))` if `pf isDefinedAt x`, `None` otherwise. */ - def condOpt[T,U](x: T)(pf: PartialFunction[T, U]): Option[U] = - if (pf isDefinedAt x) Some(pf(x)) else None + def condOpt[T,U](x: T)(pf: PartialFunction[T, U]): Option[U] = pf.lift(x) } diff --git a/src/library/scala/runtime/AbstractPartialFunction.scala b/src/library/scala/runtime/AbstractPartialFunction.scala index cbe778f09b..2e435d8a7e 100644 --- a/src/library/scala/runtime/AbstractPartialFunction.scala +++ b/src/library/scala/runtime/AbstractPartialFunction.scala @@ -8,45 +8,61 @@ package scala.runtime -import scala.annotation.unchecked.uncheckedVariance - -/** This class provides a default implementation of partial functions - * that is used for all partial function literals. - * It contains an optimized `orElse` method which supports - * chained `orElse` in linear time, and with no slow-down - * if the `orElse` part is not needed. - * The implementation of `orElse` works by cloning the abstract function object - * and modifying a private `fallBack` variable that encodes the `getorElse` part. +/** `AbstractPartialFunction` reformulates all operations of its supertrait `PartialFunction` in terms of `isDefinedAt` and `applyOrElse`. + * + * This allows more efficient implementations in many cases: + * - optimized `orElse` method supports chained `orElse` in linear time, + * and with no slow-down if the `orElse` part is not needed. + * - optimized `lift` method helps to avoid double evaluation of pattern matchers & guards + * of partial function literals. + * + * This trait is used as a basis for implementation of all partial function literals + * with non-exhaustive matchers. + * + * Use of `AbstractPartialFunction` instead of `PartialFunction` as a base trait for + * user-defined partial functions may result in better performance + * and more predictable behavior w.r.t. side effects. + * + * @author Pavel Pavlov + * @since 2.10 */ -abstract class AbstractPartialFunction[-T1, +R] - extends AbstractFunction1[T1, R] - with PartialFunction[T1, R] - with Cloneable { - - private var fallBackField: PartialFunction[T1 @uncheckedVariance, R @uncheckedVariance] = _ +abstract class AbstractPartialFunction[@specialized(scala.Int, scala.Long, scala.Float, scala.Double, scala.AnyRef) -T1, @specialized(scala.Unit, scala.Boolean, scala.Int, scala.Float, scala.Long, scala.Double, scala.AnyRef) +R] extends Function1[T1, R] with PartialFunction[T1, R] { self => + // this method must be overridden for better performance, + // for backwards compatibility, fall back to the one inherited from PartialFunction + // this assumes the old-school partial functions override the apply method, though + // override def applyOrElse[A1 <: T1, B1 >: R](x: A1, default: A1 => B1): B1 = ??? - def fallBack: PartialFunction[T1, R] = synchronized { - if (fallBackField eq null) fallBackField = PartialFunction.empty - fallBackField - } + // probably okay to make final since classes compiled before have overridden against the old version of AbstractPartialFunction + // let's not make it final so as not to confuse anyone + /*final*/ def apply(x: T1): R = applyOrElse(x, PartialFunction.empty) - override protected def missingCase(x: T1): R = fallBack(x) - - // Question: Need to ensure that fallBack is overwritten before any access - // Is the `synchronized` here the right thing to achieve this? - // Is there a cheaper way? - override def orElse[A1 <: T1, B1 >: R](that: PartialFunction[A1, B1]) : PartialFunction[A1, B1] = { - val result = this.clone.asInstanceOf[AbstractPartialFunction[A1, B1]] - result.synchronized { - result.fallBackField = if (this.fallBackField eq null) that else this.fallBackField orElse that - result + override final def andThen[C](k: R => C) : PartialFunction[T1, C] = + new AbstractPartialFunction[T1, C] { + def isDefinedAt(x: T1): Boolean = self.isDefinedAt(x) + override def applyOrElse[A1 <: T1, C1 >: C](x: A1, default: A1 => C1): C1 = + self.applyOrElse(x, PartialFunction.fallbackToken) match { + case PartialFunction.FallbackToken => default(x) + case z => k(z) + } } - } - - def isDefinedAt(x: T1): scala.Boolean = _isDefinedAt(x) || fallBack.isDefinedAt(x) - def _isDefinedAt(x: T1): scala.Boolean + // TODO: remove + protected def missingCase(x: T1): R = throw new MatchError(x) } - +/** `AbstractTotalFunction` is a partial function whose `isDefinedAt` method always returns `true`. + * + * This class is used as base class for partial function literals with + * certainly exhaustive pattern matchers. + * + * @author Pavel Pavlov + * @since 2.10 + */ +abstract class AbstractTotalFunction[@specialized(scala.Int, scala.Long, scala.Float, scala.Double, scala.AnyRef) -T1, @specialized(scala.Unit, scala.Boolean, scala.Int, scala.Float, scala.Long, scala.Double, scala.AnyRef) +R] extends Function1[T1, R] with PartialFunction[T1, R] { + final def isDefinedAt(x: T1): Boolean = true + override final def applyOrElse[A1 <: T1, B1 >: R](x: A1, default: A1 => B1): B1 = apply(x) + override final def orElse[A1 <: T1, B1 >: R](that: PartialFunction[A1, B1]): PartialFunction[A1, B1] = this + //TODO: check generated code for PF literal here + override final def andThen[C](k: R => C): PartialFunction[T1, C] = { case x => k(apply(x)) } +} diff --git a/src/library/scala/util/control/Exception.scala b/src/library/scala/util/control/Exception.scala index 5e3f8b6451..20a179a884 100644 --- a/src/library/scala/util/control/Exception.scala +++ b/src/library/scala/util/control/Exception.scala @@ -230,8 +230,5 @@ object Exception { classes exists (_ isAssignableFrom x.getClass) private def pfFromExceptions(exceptions: Class[_]*): PartialFunction[Throwable, Nothing] = - new scala.runtime.AbstractPartialFunction[Throwable, Nothing] { - def apply(x: Throwable) = throw x - def _isDefinedAt(x: Throwable) = wouldMatch(x, exceptions) - } + { case x if wouldMatch(x, exceptions) => throw x } } |