Scala example source code file (SimpleHistory.scala)

This example Scala source code file (SimpleHistory.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

buffer, charsequence, collection, compiler, entry, int, internal, jentry, jiterator, jlistiterator, mutable, nsc, string, unit

The SimpleHistory.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author Paul Phillips
 */

package scala.tools.nsc
package interpreter
package session

import scala.collection.mutable.{ Buffer, ListBuffer }
import scala.collection.JavaConverters._

class SimpleHistory extends JLineHistory {
  private var _index: Int = 0
  private val buf: Buffer[String] = new ListBuffer[String]
  private def toEntries(): Seq[JEntry] = buf.zipWithIndex map { case (x, i) => Entry(i, x) }
  private def setTo(num: Int)          = { _index = num ; true }
  private def minusOne                 = { _index -= 1 ; true }
  private def plusOne                  = { _index += 1 ; true }
  private def lastIndex                = size - 1
  private def fail(msg: String): String = {
    repldbg("Internal error in history(size %d, index %d): %s".format(
      size, index, msg)
    )
    ""
  }

  case class Entry(index: Int, value: CharSequence) extends JEntry {
    override def toString = value
  }

  def maxSize: Int = 2500
  def last = if (isEmpty) fail("last") else buf.last

  def size = buf.size
  def index = _index
  def isEmpty = buf.isEmpty
  def clear() = buf.clear()
  def get(idx: Int): CharSequence = buf(idx)
  def add(item: CharSequence): Unit = buf += item
  def replace(item: CharSequence): Unit = {
    buf trimEnd 1
    add(item)
  }
  def entries(idx: Int): JListIterator[JEntry] = toEntries().asJava.listIterator(idx)
  def entries(): JListIterator[JEntry]         = toEntries().asJava.listIterator()
  def iterator: JIterator[JEntry]              = toEntries().iterator.asJava

  def remove(idx: Int): CharSequence        = buf remove idx
  def removeFirst(): CharSequence           = buf remove 0
  def removeLast(): CharSequence            = buf remove lastIndex
  def set(idx: Int, to: CharSequence): Unit = buf(idx) = to

  def current()         = if (index >= 0 && index < buf.size) buf(index) else fail("current()")
  def previous()        = (index > 0) && minusOne
  def next()            = (index <= lastIndex) && plusOne
  def moveToFirst()     = (size > 0) && (index != 0) && setTo(0)
  def moveToLast()      = (size > 0) && (index < lastIndex) && setTo(lastIndex)
  def moveTo(idx: Int)  = (idx > 0) && (idx <= lastIndex) && setTo(idx)
  def moveToEnd(): Unit = setTo(size)

  def asStrings = buf.toList
}