Scala example source code file (Document.scala)

This example Scala source code file (Document.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

docbreak, doccons, docgroup, docnil, doctext, document, int, list, string, text, this

The Document.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala.text

import java.io.Writer

@deprecated("This object will be removed.", "2.11.0")
case object DocNil extends Document
@deprecated("This object will be removed.", "2.11.0")
case object DocBreak extends Document
@deprecated("This class will be removed.", "2.11.0")
case class DocText(txt: String) extends Document
@deprecated("This class will be removed.", "2.11.0")
case class DocGroup(doc: Document) extends Document
@deprecated("This class will be removed.", "2.11.0")
case class DocNest(indent: Int, doc: Document) extends Document
@deprecated("This class will be removed.", "2.11.0")
case class DocCons(hd: Document, tl: Document) extends Document

/**
 * A basic pretty-printing library, based on Lindig's strict version
 * of Wadler's adaptation of Hughes' pretty-printer.
 *
 * @author Michel Schinz
 * @version 1.0
 */
@deprecated("This class will be removed.", "2.11.0")
abstract class Document {
  def ::(hd: Document): Document = DocCons(hd, this)
  def ::(hd: String): Document = DocCons(DocText(hd), this)
  def :/:(hd: Document): Document = hd :: DocBreak :: this
  def :/:(hd: String): Document = hd :: DocBreak :: this

  /**
   * Format this document on `writer` and try to set line
   * breaks so that the result fits in `width` columns.
   */
  def format(width: Int, writer: Writer) {
    type FmtState = (Int, Boolean, Document)

    def fits(w: Int, state: List[FmtState]): Boolean = state match {
      case _ if w < 0 =>
        false
      case List() =>
        true
      case (_, _, DocNil) :: z =>
        fits(w, z)
      case (i, b, DocCons(h, t)) :: z =>
        fits(w, (i,b,h) :: (i,b,t) :: z)
      case (_, _, DocText(t)) :: z =>
        fits(w - t.length(), z)
      case (i, b, DocNest(ii, d)) :: z =>
        fits(w, (i + ii, b, d) :: z)
      case (_, false, DocBreak) :: z =>
        fits(w - 1, z)
      case (_, true, DocBreak) :: z =>
        true
      case (i, _, DocGroup(d)) :: z =>
        fits(w, (i, false, d) :: z)
    }

    def spaces(n: Int) {
      var rem = n
      while (rem >= 16) { writer write "                "; rem -= 16 }
      if (rem >= 8)     { writer write "        "; rem -= 8 }
      if (rem >= 4)     { writer write "    "; rem -= 4 }
      if (rem >= 2)     { writer write "  "; rem -= 2}
      if (rem == 1)     { writer write " " }
    }

    def fmt(k: Int, state: List[FmtState]): Unit = state match {
      case List() => ()
      case (_, _, DocNil) :: z =>
        fmt(k, z)
      case (i, b, DocCons(h, t)) :: z =>
        fmt(k, (i, b, h) :: (i, b, t) :: z)
      case (i, _, DocText(t)) :: z =>
        writer write t
        fmt(k + t.length(), z)
      case (i, b, DocNest(ii, d)) :: z =>
        fmt(k, (i + ii, b, d) :: z)
      case (i, true, DocBreak) :: z =>
        writer write "\n"
        spaces(i)
        fmt(i, z)
      case (i, false, DocBreak) :: z =>
        writer write " "
        fmt(k + 1, z)
      case (i, b, DocGroup(d)) :: z =>
        val fitsFlat = fits(width - k, (i, false, d) :: z)
        fmt(k, (i, !fitsFlat, d) :: z)
      case _ =>
        ()
    }

    fmt(0, (0, false, DocGroup(this)) :: Nil)
  }
}

@deprecated("This object will be removed.", "2.11.0")
object Document {
  /** The empty document */
  def empty = DocNil

  /** A break, which will either be turned into a space or a line break */
  def break = DocBreak

  /** A document consisting of some text literal */
  def text(s: String): Document = DocText(s)

  /**
   * A group, whose components will either be printed with all breaks
   * rendered as spaces, or with all breaks rendered as line breaks.
   */
  def group(d: Document): Document = DocGroup(d)

  /** A nested document, which will be indented as specified. */
  def nest(i: Int, d: Document): Document = DocNest(i, d)
}