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// -----------------------------------------------------------------------------
//
// Scalax - The Scala Community Library
// Copyright (c) 2005-8 The Scalax Project. All rights reserved.
//
// The primary distribution site is http://scalax.scalaforge.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.json4s.scalap
/** A Rule is a function from some input to a Result. The result may be:
*
*
Success, with a value of some type and an output that may serve as the input to subsequent rules.
*
Failure. A failure may result in some alternative rule being applied.
*
Error. No further rules should be attempted.
*
*
* @author Andrew Foggin
*
* Inspired by the Scala parser combinator.
*/
trait Rule[-In, +Out, +A, +X] extends (In => Result[Out, A, X]) {
val factory: Rules
import factory._
def as(name: String) = ruleWithName(name, this)
def flatMap[Out2, B, X2 >: X](fa2ruleb: A => Out => Result[Out2, B, X2]) = mapResult {
case Success(out, a) => fa2ruleb(a)(out)
case Failure => Failure
case err @ Error(_) => err
}
def map[B](fa2b: A => B) = flatMap { a => out => Success(out, fa2b(a)) }
def filter(f: A => Boolean) = flatMap { a => out => if(f(a)) Success(out, a) else Failure }
def mapResult[Out2, B, Y](f: Result[Out, A, X] => Result[Out2, B, Y]) = rule {
in: In => f(apply(in))
}
def orElse[In2 <: In, Out2 >: Out, A2 >: A, X2 >: X](other: => Rule[In2, Out2, A2, X2]): Rule[In2, Out2, A2, X2] = new Choice[In2, Out2, A2, X2] {
val factory = Rule.this.factory
lazy val choices = Rule.this :: other :: Nil
}
def orError[In2 <: In] = this orElse error[Any]
def |[In2 <: In, Out2 >: Out, A2 >: A, X2 >: X](other: => Rule[In2, Out2, A2, X2]) = orElse(other)
def ^^[B](fa2b: A => B) = map(fa2b)
def ^^?[B](pf: PartialFunction[A, B]) = filter (pf.isDefinedAt(_)) ^^ pf
def ??(pf: PartialFunction[A, Any]) = filter (pf.isDefinedAt(_))
def -^[B](b: B) = map { any => b }
/** Maps an Error */
def !^[Y](fx2y: X => Y) = mapResult {
case s @ Success(_, _) => s
case Failure => Failure
case Error(x) => Error(fx2y(x))
}
def >>[Out2, B, X2 >: X](fa2ruleb: A => Out => Result[Out2, B, X2]) = flatMap(fa2ruleb)
def >->[Out2, B, X2 >: X](fa2resultb: A => Result[Out2, B, X2]) = flatMap { a => any => fa2resultb(a) }
def >>?[Out2, B, X2 >: X](pf: PartialFunction[A, Rule[Out, Out2, B, X2]]) = filter(pf isDefinedAt _) flatMap pf
def >>&[B, X2 >: X](fa2ruleb: A => Out => Result[Any, B, X2]) = flatMap { a => out => fa2ruleb(a)(out) mapOut { any => out } }
def ~[Out2, B, X2 >: X](next: => Rule[Out, Out2, B, X2]) = for (a <- this; b <- next) yield new ~(a, b)
def ~-[Out2, B, X2 >: X](next: => Rule[Out, Out2, B, X2]) = for (a <- this; b <- next) yield a
def -~[Out2, B, X2 >: X](next: => Rule[Out, Out2, B, X2]) = for (a <- this; b <- next) yield b
def ~++[Out2, B >: A, X2 >: X](next: => Rule[Out, Out2, Seq[B], X2]) = for (a <- this; b <- next) yield a :: b.toList
/** Apply the result of this rule to the function returned by the next rule */
def ~>[Out2, B, X2 >: X](next: => Rule[Out, Out2, A => B, X2]) = for (a <- this; fa2b <- next) yield fa2b(a)
/** Apply the result of this rule to the function returned by the previous rule */
def <~:[InPrev, B, X2 >: X](prev: => Rule[InPrev, In, A => B, X2]) = for (fa2b <- prev; a <- this) yield fa2b(a)
def ~ = for (a <- this; b <- next.orError) yield new ~(a, b)
def ~- = for (a <- this; b <- next.orError) yield a
def -~ = for (a <- this; b <- next.orError) yield b
def -[In2 <: In](exclude: => Rule[In2, Any, Any, Any]) = !exclude -~ this
/** ^~^(f) is equivalent to ^^ { case b1 ~ b2 => f(b1, b2) }
*/
def ^~^[B1, B2, B >: A, C](f: (B1, B2) => C)(implicit A: A => (B1 ~ B2)) = map { a =>
(a: B1 ~ B2) match { case b1 ~ b2 => f(b1, b2) }
}
/** ^~~^(f) is equivalent to ^^ { case b1 ~ b2 ~ b3 => f(b1, b2, b3) }
*/
def ^~~^[B1, B2, B3, B >: A, C](f: (B1, B2, B3) => C)(implicit A: A => (B1 ~ B2 ~ B3)) = map { a =>
(a: B1 ~ B2 ~ B3) match { case b1 ~ b2 ~ b3 => f(b1, b2, b3) }
}
/** ^~~~^(f) is equivalent to ^^ { case b1 ~ b2 ~ b3 ~ b4 => f(b1, b2, b3, b4) }
*/
def ^~~~^[B1, B2, B3, B4, B >: A, C](f: (B1, B2, B3, B4) => C)(implicit A: A => (B1 ~ B2 ~ B3 ~ B4)) = map { a =>
(a: B1 ~ B2 ~ B3 ~ B4) match { case b1 ~ b2 ~ b3 ~ b4 => f(b1, b2, b3, b4) }
}
/** ^~~~~^(f) is equivalent to ^^ { case b1 ~ b2 ~ b3 ~ b4 ~ b5 => f(b1, b2, b3, b4, b5) }
*/
def ^~~~~^[B1, B2, B3, B4, B5, B >: A, C](f: (B1, B2, B3, B4, B5) => C)(implicit A: A => (B1 ~ B2 ~ B3 ~ B4 ~ B5)) = map { a =>
(a: B1 ~ B2 ~ B3 ~ B4 ~ B5) match { case b1 ~ b2 ~ b3 ~ b4 ~ b5 => f(b1, b2, b3, b4, b5) }
}
/** ^~~~~~^(f) is equivalent to ^^ { case b1 ~ b2 ~ b3 ~ b4 ~ b5 ~ b6 => f(b1, b2, b3, b4, b5, b6) }
*/
def ^~~~~~^[B1, B2, B3, B4, B5, B6, B >: A, C](f: (B1, B2, B3, B4, B5, B6) => C)(implicit A: A => (B1 ~ B2 ~ B3 ~ B4 ~ B5 ~ B6)) = map { a =>
(a: B1 ~ B2 ~ B3 ~ B4 ~ B5 ~ B6) match { case b1 ~ b2 ~ b3 ~ b4 ~ b5 ~ b6 => f(b1, b2, b3, b4, b5, b6) }
}
/** ^~~~~~~^(f) is equivalent to ^^ { case b1 ~ b2 ~ b3 ~ b4 ~ b5 ~ b6 => f(b1, b2, b3, b4, b5, b6) }
*/
def ^~~~~~~^[B1, B2, B3, B4, B5, B6, B7, B >: A, C](f: (B1, B2, B3, B4, B5, B6, B7) => C)(implicit A: A => (B1 ~ B2 ~ B3 ~ B4 ~ B5 ~ B6 ~ B7)) = map { a =>
(a: B1 ~ B2 ~ B3 ~ B4 ~ B5 ~ B6 ~ B7) match { case b1 ~ b2 ~ b3 ~ b4 ~ b5 ~ b6 ~b7 => f(b1, b2, b3, b4, b5, b6, b7) }
}
/** >~>(f) is equivalent to >> { case b1 ~ b2 => f(b1, b2) }
*/
def >~>[Out2, B1, B2, B >: A, C, X2 >: X](f: (B1, B2) => Out => Result[Out2, C, X2])(implicit A: A => (B1 ~ B2)) = flatMap { a =>
(a: B1 ~ B2) match { case b1 ~ b2 => f(b1, b2) }
}
/** ^-^(f) is equivalent to ^^ { b2 => b1 => f(b1, b2) }
*/
def ^-^ [B1, B2 >: A, C](f: (B1, B2) => C) = map { b2: B2 => b1: B1 => f(b1, b2) }
/** ^~>~^(f) is equivalent to ^^ { case b2 ~ b3 => b1 => f(b1, b2, b3) }
*/
def ^~>~^ [B1, B2, B3, B >: A, C](f: (B1, B2, B3) => C)(implicit A: A => (B2 ~ B3)) = map { a =>
(a: B2 ~ B3) match { case b2 ~ b3 => b1: B1 => f(b1, b2, b3) }
}
}
trait Choice[-In, +Out, +A, +X] extends Rule[In, Out, A, X] {
def choices: List[Rule[In, Out, A, X]]
def apply(in: In) = {
def oneOf(list: List[Rule[In, Out, A, X]]): Result[Out, A, X] = list match {
case Nil => Failure
case first :: rest => first(in) match {
case Failure => oneOf(rest)
case result => result
}
}
oneOf(choices)
}
override def orElse[In2 <: In, Out2 >: Out, A2 >: A, X2 >: X](other: => Rule[In2, Out2, A2, X2]): Rule[In2, Out2, A2, X2] = new Choice[In2, Out2, A2, X2] {
val factory = Choice.this.factory
lazy val choices = Choice.this.choices ::: other :: Nil
}
}
