/
Document.scala
117 lines (103 loc) · 3.79 KB
/
Document.scala
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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2011, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.text
import java.io.Writer
case object DocNil extends Document
case object DocBreak extends Document
case class DocText(txt: String) extends Document
case class DocGroup(doc: Document) extends Document
case class DocNest(indent: Int, doc: Document) extends Document
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
*/
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)
}
}
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)
}