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Scala example source code file (ImplicitConversions.scala)

This example Scala source code file (ImplicitConversions.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

a, a, b, b, c, c, d, d, e, f, list, option, parsers, t

The Scala ImplicitConversions.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2006-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |                                         **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */


package scala.util.parsing.combinator

/** This object contains implicit conversions that come in handy when using the `^^' combinator 
 * {@see Parsers} to construct an AST from the concrete syntax.
 *<p>
 * The reason for this is that the sequential composition combinator (`~') combines its constituents
 * into a ~. When several `~'s are combined, this results in nested `~'s (to the left).
 * The `flatten*' coercions makes it easy to apply an `n'-argument function to a nested ~ of
 * depth (`n-1')</p>
 *<p>
 * The `headOptionTailToFunList' converts a function that takes a List[A] to a function that 
 * accepts a ~[A, Option[List[A]]] (this happens when, e.g., parsing something of the following
 * shape: p ~ opt("." ~ repsep(p, ".")) -- where `p' is a parser that yields an A)</p>
 *
 * @author Martin Odersky, Iulian Dragos, Adriaan Moors 
 */
trait ImplicitConversions { self: Parsers => 
  implicit def flatten2[A, B, C]         (f: (A, B) => C) = 
    (p: ~[A, B]) => p match {case a ~ b => f(a, b)}
  implicit def flatten3[A, B, C, D]      (f: (A, B, C) => D) = 
    (p: ~[~[A, B], C]) => p match {case a ~ b ~ c => f(a, b, c)}
  implicit def flatten4[A, B, C, D, E]   (f: (A, B, C, D) => E) = 
    (p: ~[~[~[A, B], C], D]) => p match {case a ~ b ~ c ~ d => f(a, b, c, d)}
  implicit def flatten5[A, B, C, D, E, F](f: (A, B, C, D, E) => F) = 
    (p: ~[~[~[~[A, B], C], D], E]) => p match {case a ~ b ~ c ~ d ~ e=> f(a, b, c, d, e)}
  implicit def headOptionTailToFunList[A, T] (f: List[A] => T)= 
    (p: ~[A, Option[List[A]]]) => f(p._1 :: (p._2 match { case Some(xs) => xs case None => Nil}))
}

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