Scala example source code file (Chars.scala)

This example Scala source code file (Chars.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

a, annotation, boolean, char, chars, cr, ff, int, lf, string, su

The Chars.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2006-2013 LAMP/EPFL
 * @author  Martin Odersky
 */
package scala
package reflect
package internal

import scala.annotation.{ tailrec, switch }
import java.lang.{ Character => JCharacter }
import scala.language.postfixOps

/** Contains constants and classifier methods for characters */
trait Chars {
  // Be very careful touching these.
  // Apparently trivial changes to the way you write these constants
  // will cause Scanners.scala to go from a nice efficient switch to
  // a ghastly nested if statement which will bring the type checker
  // to its knees. See ticket #1456
  // Martin: (this should be verified now that the pattern rules have been redesigned).
  final val LF = '\u000A'
  final val FF = '\u000C'
  final val CR = '\u000D'
  final val SU = '\u001A'

  /** Convert a character digit to an Int according to given base,
   *  -1 if no success
   */
  def digit2int(ch: Char, base: Int): Int = {
    val num = (
      if (ch <= '9') ch - '0'
      else if ('a' <= ch && ch <= 'z') ch - 'a' + 10
      else if ('A' <= ch && ch <= 'Z') ch - 'A' + 10
      else -1
    )
    if (0 <= num && num < base) num else -1
  }
  /** Buffer for creating '\ u XXXX' strings. */
  private[this] val char2uescapeArray = Array[Char]('\\', 'u', 0, 0, 0, 0)

  /** Convert a character to a backslash-u escape */
  def char2uescape(c: Char): String = {
    @inline def hexChar(ch: Int): Char =
      ( if (ch < 10) '0' else 'A' - 10 ) + ch toChar

    char2uescapeArray(2) = hexChar((c >> 12)     )
    char2uescapeArray(3) = hexChar((c >>  8) % 16)
    char2uescapeArray(4) = hexChar((c >>  4) % 16)
    char2uescapeArray(5) = hexChar((c      ) % 16)

    new String(char2uescapeArray)
  }

  /** Is character a line break? */
  def isLineBreakChar(c: Char) = (c: @switch) match {
    case LF|FF|CR|SU  => true
    case _            => false
  }

  /** Is character a whitespace character (but not a new line)? */
  def isWhitespace(c: Char) =
    c == ' ' || c == '\t' || c == CR

  /** Can character form part of a doc comment variable $xxx? */
  def isVarPart(c: Char) =
    '0' <= c && c <= '9' || 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z'

  /** Can character start an alphanumeric Scala identifier? */
  def isIdentifierStart(c: Char): Boolean =
    (c == '_') || (c == '$') || Character.isUnicodeIdentifierStart(c)

  /** Can character form part of an alphanumeric Scala identifier? */
  def isIdentifierPart(c: Char) =
    (c == '$') || Character.isUnicodeIdentifierPart(c)

  /** Is character a math or other symbol in Unicode?  */
  def isSpecial(c: Char) = {
    val chtp = Character.getType(c)
    chtp == Character.MATH_SYMBOL.toInt || chtp == Character.OTHER_SYMBOL.toInt
  }

  private final val otherLetters = Set[Char]('\u0024', '\u005F')  // '$' and '_'
  private final val letterGroups = {
    import JCharacter._
    Set[Byte](LOWERCASE_LETTER, UPPERCASE_LETTER, OTHER_LETTER, TITLECASE_LETTER, LETTER_NUMBER)
  }
  def isScalaLetter(ch: Char) = letterGroups(JCharacter.getType(ch).toByte) || otherLetters(ch)

  /** Can character form part of a Scala operator name? */
  def isOperatorPart(c : Char) : Boolean = (c: @switch) match {
    case '~' | '!' | '@' | '#' | '%' |
         '^' | '*' | '+' | '-' | '<' |
         '>' | '?' | ':' | '=' | '&' |
         '|' | '/' | '\\' => true
    case c => isSpecial(c)
  }
}

object Chars extends Chars { }