Scala example source code file (Regex.scala)

This example Scala source code file (Regex.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

charsequence, collection, int, iterator, match, matcher, none, option, regex, some, string

The Regex.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2007-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */


/**
 * This package is concerned with regular expression (regex) matching against strings,
 * with the main goal of pulling out information from those matches, or replacing
 * them with something else.
 *
 * There are four classes and three objects, with most of them being members of
 * Regex companion object. [[scala.util.matching.Regex]] is the class users instantiate
 * to do regular expression matching.
 *
 * The remaining classes and objects in the package are used in the following way:
 *
 * * The companion object to [[scala.util.matching.Regex]] just contains the other members.
 * * [[scala.util.matching.Regex.Match]] makes more information about a match available.
 * * [[scala.util.matching.Regex.MatchIterator]] is used to iterate over multiple matches.
 * * [[scala.util.matching.Regex.MatchData]] is just a base trait for the above classes.
 * * [[scala.util.matching.Regex.Groups]] extracts group from a [[scala.util.matching.Regex.Match]]
 *   without recomputing the match.
 * * [[scala.util.matching.Regex.Match]] converts a [[scala.util.matching.Regex.Match]]
 *   into a [[java.lang.String]].
 *
 */
package scala
package util.matching

import scala.collection.AbstractIterator
import java.util.regex.{ Pattern, Matcher }

/** This class provides methods for creating and using regular expressions.
 *  It is based on the regular expressions of the JDK since 1.4.
 *
 *  Its main goal is to extract strings that match a pattern, or the subgroups
 *  that make it up. For that reason, it is usually used with for comprehensions
 *  and matching (see methods for examples).
 *
 *  A Regex is created from a [[java.lang.String]] representation of the
 *  regular expression pattern^1^. That pattern is compiled
 *  during construction, so frequently used patterns should be declared outside
 *  loops if performance is of concern. Possibly, they might be declared on a
 *  companion object, so that they need only to be initialized once.
 *
 *  The canonical way of creating regex patterns is by using the method `r`, provided
 *  on [[java.lang.String]] through an implicit conversion into
 *  [[scala.collection.immutable.WrappedString]]. Using triple quotes to write these
 *  strings avoids having to quote the backslash character (`\`).
 *
 *  Using the constructor directly, on the other hand, makes
 *  it possible to declare names for subgroups in the pattern.
 *
 *  For example, both declarations below generate the same regex, but the second
 *  one associate names with the subgroups.
 *
 *  {{{
 *  val dateP1 = """(\d\d\d\d)-(\d\d)-(\d\d)""".r
 *  val dateP2 = new scala.util.matching.Regex("""(\d\d\d\d)-(\d\d)-(\d\d)""", "year", "month", "day")
 *  }}}
 *
 *  There are two ways of using a `Regex` to find a pattern: calling methods on
 *  Regex, such as `findFirstIn` or `findAllIn`, or using it as an extractor in a
 *  pattern match.
 *
 *  Note that, when calling `findAllIn`, the resulting [[scala.util.matching.Regex.MatchIterator]]
 *  needs to be initialized (by calling `hasNext` or `next()`, or causing these to be
 *  called) before information about a match can be retrieved:
 *
 *  {{{
 *  val msg = "I love Scala"
 *
 *  // val start = " ".r.findAllIn(msg).start // throws an IllegalStateException
 *
 *  val matches = " ".r.findAllIn(msg)
 *  matches.hasNext // initializes the matcher
 *  val start = matches.start
 *  }}}
 *
 *  When Regex is used as an extractor in a pattern match, note that it
 *  only succeeds if the whole text can be matched. For this reason, one usually
 *  calls a method to find the matching substrings, and then use it as an extractor
 *  to break match into subgroups.
 *
 *  As an example, the above patterns can be used like this:
 *
 *  {{{
 *  val dateP1(year, month, day) = "2011-07-15"
 *
 *  // val dateP1(year, month, day) = "Date 2011-07-15" // throws an exception at runtime
 *
 *  val copyright: String = dateP1 findFirstIn "Date of this document: 2011-07-15" match {
 *    case Some(dateP1(year, month, day)) => "Copyright "+year
 *    case None                           => "No copyright"
 *  }
 *
 *  val copyright: Option[String] = for {
 *    dateP1(year, month, day) <- dateP1 findFirstIn "Last modified 2011-07-15"
 *  } yield year

 *  def getYears(text: String): Iterator[String] = for (dateP1(year, _, _) <- dateP1 findAllIn text) yield year
 *  def getFirstDay(text: String): Option[String] = for (m <- dateP2 findFirstMatchIn text) yield m group "day"
 *  }}}
 *
 *  Regex does not provide a method that returns a [[scala.Boolean]]. One can
 *  use [[java.lang.String]] `matches` method, or, if `Regex` is preferred,
 *  either ignore the return value or test the `Option` for emptyness. For example:
 *
 *  {{{
 *  def hasDate(text: String): Boolean = (dateP1 findFirstIn text).nonEmpty
 *  def printLinesWithDates(lines: Traversable[String]) {
 *    lines foreach { line =>
 *      dateP1 findFirstIn line foreach { _ => println(line) }
 *    }
 *  }
 *  }}}
 *
 *  There are also methods that can be used to replace the patterns
 *  on a text. The substitutions can be simple replacements, or more
 *  complex functions. For example:
 *
 *  {{{
 *  val months = Map( 1 -> "Jan", 2 -> "Feb", 3 -> "Mar",
 *                    4 -> "Apr", 5 -> "May", 6 -> "Jun",
 *                    7 -> "Jul", 8 -> "Aug", 9 -> "Sep",
 *                    10 -> "Oct", 11 -> "Nov", 12 -> "Dec")
 *
 *  import scala.util.matching.Regex.Match
 *  def reformatDate(text: String) = dateP2 replaceAllIn ( text, (m: Match) =>
 *    "%s %s, %s" format (months(m group "month" toInt), m group "day", m group "year")
 *  )
 *  }}}
 *
 *  You can use special pattern syntax constructs like `(?idmsux-idmsux)`¹ to switch
 *  various regex compilation options like `CASE_INSENSITIVE` or `UNICODE_CASE`.
 *
 *  @note ¹ A detailed description is available in [[java.util.regex.Pattern]].
 *  @see [[java.util.regex.Pattern]]
 *
 *  @author  Thibaud Hottelier
 *  @author  Philipp Haller
 *  @author  Martin Odersky
 *  @version 1.1, 29/01/2008
 *
 *  @param pattern    The compiled pattern
 *  @param groupNames A mapping from names to indices in capture groups
 *
 *  @define replacementString
 *  In the replacement String, a dollar sign (`$`) followed by a number will be
 *  interpreted as a reference to a group in the matched pattern, with numbers
 *  1 through 9 corresponding to the first nine groups, and 0 standing for the
 *  whole match. Any other character is an error. The backslash (`\`) character
 *  will be interpreted as an escape character, and can be used to escape the
 *  dollar sign. One can use [[scala.util.matching.Regex]]'s `quoteReplacement`
 *  to automatically escape these characters.
 */
@SerialVersionUID(-2094783597747625537L)
class Regex private[matching](val pattern: Pattern, groupNames: String*) extends Serializable {
  outer =>

  import Regex._

  /**
    *  @param regex      A string representing a regular expression
    *  @param groupNames A mapping from names to indices in capture groups
    */
  def this(regex: String, groupNames: String*) = this(Pattern.compile(regex), groupNames: _*)

  /** Tries to match a [[java.lang.CharSequence]].
   *  If the match succeeds, the result is a list of the matching
   *  groups (or a `null` element if a group did not match any input).
   *  If the pattern specifies no groups, then the result will be an empty list
   *  on a successful match.
   *
   *  This method attempts to match the entire input by default; to find the next
   *  matching subsequence, use an unanchored Regex.

   *  For example:
   *
   *  {{{
   *  val p1 = "ab*c".r
   *  val p1Matches = "abbbc" match {
   *    case p1() => true
   *    case _    => false
   *  }
   *  val p2 = "a(b*)c".r
   *  val numberOfB = "abbbc" match {
   *    case p2(b) => Some(b.length)
   *    case _     => None
   *  }
   *  val p3 = "b*".r.unanchored
   *  val p3Matches = "abbbc" match {
   *    case p3() => true
   *    case _    => false
   *  }
   *  }}}
   *
   *  @param  s     The string to match
   *  @return       The matches
   */
  def unapplySeq(s: CharSequence): Option[List[String]] = {
    val m = pattern matcher s
    if (runMatcher(m)) Some((1 to m.groupCount).toList map m.group)
    else None
  }

  /** Tries to match the String representation of a [[scala.Char]].
   *  If the match succeeds, the result is the first matching
   *  group if any groups are defined, or an empty Sequence otherwise.
   *
   *  For example:
   *
   *  {{{
   *  val cat = "cat"
   *  // the case must consume the group to match
   *  val r = """(\p{Lower})""".r
   *  cat(0) match { case r(x) => true }
   *  cat(0) match { case r(_) => true }
   *  cat(0) match { case r(_*) => true }
   *  cat(0) match { case r() => true }     // no match
   *
   *  // there is no group to extract
   *  val r = """\p{Lower}""".r
   *  cat(0) match { case r(x) => true }    // no match
   *  cat(0) match { case r(_) => true }    // no match
   *  cat(0) match { case r(_*) => true }   // matches
   *  cat(0) match { case r() => true }     // matches
   *
   *  // even if there are multiple groups, only one is returned
   *  val r = """((.))""".r
   *  cat(0) match { case r(_) => true }    // matches
   *  cat(0) match { case r(_,_) => true }  // no match
   *  }}}
   *
   *  @param  c     The Char to match
   *  @return       The match
   */
  def unapplySeq(c: Char): Option[List[Char]] = {
    val m = pattern matcher c.toString
    if (runMatcher(m)) {
      if (m.groupCount > 0) Some((m group 1).toList) else Some(Nil)
    } else None
  }

  /** Tries to match on a [[scala.util.matching.Regex.Match]].
   *  A previously failed match results in None.
   *  If a successful match was made against the current pattern, then that result is used.
   *  Otherwise, this Regex is applied to the previously matched input,
   *  and the result of that match is used.
   */
  def unapplySeq(m: Match): Option[List[String]] =
    if (m.matched == null) None
    else if (m.matcher.pattern == this.pattern) Some((1 to m.groupCount).toList map m.group)
    else unapplySeq(m.matched)

  /** Tries to match target.
   *  @param target The string to match
   *  @return       The matches
   */
  @deprecated("Extracting a match result from anything but a CharSequence or Match is deprecated", "2.11.0")
  def unapplySeq(target: Any): Option[List[String]] = target match {
    case s: CharSequence =>
      val m = pattern matcher s
      if (runMatcher(m)) Some((1 to m.groupCount).toList map m.group)
      else None
    case m: Match => unapplySeq(m.matched)
    case _ => None
  }

  //  @see UnanchoredRegex
  protected def runMatcher(m: Matcher) = m.matches()

  /** Return all matches of this regexp in given character sequence as a [[scala.util.matching.Regex.MatchIterator]],
   *  which is a special [[scala.collection.Iterator]] that returns the
   *  matched strings, but can also be converted into a normal iterator
   *  that returns objects of type [[scala.util.matching.Regex.Match]]
   *  that can be queried for data such as the text that precedes the
   *  match, subgroups, etc.
   *
   *  Attempting to retrieve information about a match before initializing
   *  the iterator can result in [[java.lang.IllegalStateException]]s. See
   *  [[scala.util.matching.Regex.MatchIterator]] for details.
   *
   *  @param source The text to match against.
   *  @return       A [[scala.util.matching.Regex.MatchIterator]] of all matches.
   *  @example      {{{for (words <- """\w+""".r findAllIn "A simple example.") yield words}}}
   */
  def findAllIn(source: CharSequence) = new Regex.MatchIterator(source, this, groupNames)


  /** Return all matches of this regexp in given character sequence as a
   *  [[scala.collection.Iterator]] of [[scala.util.matching.Regex.Match]].
   *
   *  @param source The text to match against.
   *  @return       A [[scala.collection.Iterator]] of [[scala.util.matching.Regex.Match]] for all matches.
   *  @example      {{{for (words <- """\w+""".r findAllMatchIn "A simple example.") yield words.start}}}
   */
  def findAllMatchIn(source: CharSequence): Iterator[Match] = {
    val matchIterator = findAllIn(source)
    new Iterator[Match] {
      def hasNext = matchIterator.hasNext
      def next: Match = {
        matchIterator.next()
        new Match(matchIterator.source, matchIterator.matcher, matchIterator.groupNames).force
      }
    }
  }

  /** Return optionally first matching string of this regexp in given character sequence,
   *  or None if it does not exist.
   *
   *  @param source The text to match against.
   *  @return       An [[scala.Option]] of the first matching string in the text.
   *  @example      {{{"""\w+""".r findFirstIn "A simple example." foreach println // prints "A"}}}
   */
  def findFirstIn(source: CharSequence): Option[String] = {
    val m = pattern.matcher(source)
    if (m.find) Some(m.group) else None
  }

  /** Return optionally first match of this regexp in given character sequence,
   *  or None if it does not exist.
   *
   *  The main difference between this method and `findFirstIn` is that the (optional) return
   *  type for this is [[scala.util.matching.Regex.Match]], through which more
   *  data can be obtained about the match, such as the strings that precede and follow it,
   *  or subgroups.
   *
   *  @param source The text to match against.
   *  @return       A [[scala.Option]] of [[scala.util.matching.Regex.Match]] of the first matching string in the text.
   *  @example      {{{("""[a-z]""".r findFirstMatchIn "A simple example.") map (_.start) // returns Some(2), the index of the first match in the text}}}
   */
  def findFirstMatchIn(source: CharSequence): Option[Match] = {
    val m = pattern.matcher(source)
    if (m.find) Some(new Match(source, m, groupNames)) else None
  }

  /** Return optionally match of this regexp at the beginning of the
   *  given character sequence, or None if regexp matches no prefix
   *  of the character sequence.
   *
   *  The main difference from this method to `findFirstIn` is that this
   *  method will not return any matches that do not begin at the start
   *  of the text being matched against.
   *
   *  @param source The text to match against.
   *  @return       A [[scala.Option]] of the matched prefix.
   *  @example      {{{"""[a-z]""".r findPrefixOf "A simple example." // returns None, since the text does not begin with a lowercase letter}}}
   */
  def findPrefixOf(source: CharSequence): Option[String] = {
    val m = pattern.matcher(source)
    if (m.lookingAt) Some(m.group) else None
  }

  /** Return optionally match of this regexp at the beginning of the
   *  given character sequence, or None if regexp matches no prefix
   *  of the character sequence.
   *
   *  The main difference from this method to `findFirstMatchIn` is that
   *  this method will not return any matches that do not begin at the
   *  start of the text being matched against.
   *
   *  @param source The text to match against.
   *  @return       A [[scala.Option]] of the [[scala.util.matching.Regex.Match]] of the matched string.
   *  @example      {{{"""\w+""".r findPrefixMatchOf "A simple example." map (_.after) // returns Some(" simple example.")}}}
   */
  def findPrefixMatchOf(source: CharSequence): Option[Match] = {
    val m = pattern.matcher(source)
    if (m.lookingAt) Some(new Match(source, m, groupNames)) else None
  }

  /** Replaces all matches by a string.
   *
   *  $replacementString
   *
   *  @param target      The string to match
   *  @param replacement The string that will replace each match
   *  @return            The resulting string
   *  @example           {{{"""\d+""".r replaceAllIn ("July 15", "<NUMBER>") // returns "July <NUMBER>"}}}
   */
  def replaceAllIn(target: CharSequence, replacement: String): String = {
    val m = pattern.matcher(target)
    m.replaceAll(replacement)
  }

  /**
   * Replaces all matches using a replacer function. The replacer function takes a
   * [[scala.util.matching.Regex.Match]] so that extra information can be obtained
   * from the match. For example:
   *
   * {{{
   * import scala.util.matching.Regex
   * val datePattern = new Regex("""(\d\d\d\d)-(\d\d)-(\d\d)""", "year", "month", "day")
   * val text = "From 2011-07-15 to 2011-07-17"
   * val repl = datePattern replaceAllIn (text, m => m.group("month")+"/"+m.group("day"))
   * }}}
   *
   * $replacementString
   *
   * @param target      The string to match.
   * @param replacer    The function which maps a match to another string.
   * @return            The target string after replacements.
   */
  def replaceAllIn(target: CharSequence, replacer: Match => String): String = {
    val it = new Regex.MatchIterator(target, this, groupNames).replacementData
    it foreach (md => it replace replacer(md))
    it.replaced
  }

  /**
   * Replaces some of the matches using a replacer function that returns an [[scala.Option]].
   * The replacer function takes a [[scala.util.matching.Regex.Match]] so that extra
   * information can be btained from the match. For example:
   *
   * {{{
   * import scala.util.matching.Regex._
   *
   * val map = Map("x" -> "a var", "y" -> """some $ and \ signs""")
   * val text = "A text with variables %x, %y and %z."
   * val varPattern = """%(\w+)""".r
   * val mapper = (m: Match) => map get (m group 1) map (quoteReplacement(_))
   * val repl = varPattern replaceSomeIn (text, mapper)
   * }}}
   *
   * $replacementString
   *
   * @param target      The string to match.
   * @param replacer    The function which optionally maps a match to another string.
   * @return            The target string after replacements.
   */
  def replaceSomeIn(target: CharSequence, replacer: Match => Option[String]): String = {
    val it = new Regex.MatchIterator(target, this, groupNames).replacementData
    for (matchdata <- it ; replacement <- replacer(matchdata))
      it replace replacement

    it.replaced
  }

  /** Replaces the first match by a string.
   *
   *  $replacementString
   *
   *  @param target      The string to match
   *  @param replacement The string that will replace the match
   *  @return            The resulting string
   */
  def replaceFirstIn(target: CharSequence, replacement: String): String = {
    val m = pattern.matcher(target)
    m.replaceFirst(replacement)
  }

  /** Splits the provided character sequence around matches of this regexp.
   *
   *  @param toSplit The character sequence to split
   *  @return        The array of strings computed by splitting the
   *                 input around matches of this regexp
   */
  def split(toSplit: CharSequence): Array[String] =
    pattern.split(toSplit)

  /** Create a new Regex with the same pattern, but no requirement that
   *  the entire String matches in extractor patterns.  For instance, the strings
   *  shown below lead to successful matches, where they would not otherwise.
   *
   *  {{{
   *  val dateP1 = """(\d\d\d\d)-(\d\d)-(\d\d)""".r.unanchored
   *
   *  val dateP1(year, month, day) = "Date 2011-07-15"
   *
   *  val copyright: String = "Date of this document: 2011-07-15" match {
   *    case dateP1(year, month, day) => "Copyright "+year
   *    case _                        => "No copyright"
   *  }
   *  }}}
   *
   *  @return        The new unanchored regex
   */
  def unanchored: UnanchoredRegex = new Regex(pattern, groupNames: _*) with UnanchoredRegex { override def anchored = outer }
  def anchored: Regex             = this

  def regex: String = pattern.pattern

  /** The string defining the regular expression */
  override def toString = regex
}

trait UnanchoredRegex extends Regex {
  override protected def runMatcher(m: Matcher) = m.find()
  override def unanchored = this
}

/** This object defines inner classes that describe
 *  regex matches and helper objects.
 */
object Regex {

  /** This class provides methods to access
   *  the details of a match.
   */
  trait MatchData {

    /** The source from where the match originated */
    val source: CharSequence

    /** The names of the groups, or some empty sequence if one defined */
    val groupNames: Seq[String]

    /** The number of subgroups in the pattern (not all of these need to match!) */
    def groupCount: Int

    /** The index of the first matched character, or -1 if nothing was matched */
    def start: Int

    /** The index of the first matched character in group `i`,
     *  or -1 if nothing was matched for that group */
    def start(i: Int): Int

    /** The index of the last matched character, or -1 if nothing was matched */
    def end: Int

    /** The index following the last matched character in group `i`,
     *  or -1 if nothing was matched for that group */
    def end(i: Int): Int

    /** The matched string, or `null` if nothing was matched */
    def matched: String =
      if (start >= 0) source.subSequence(start, end).toString
      else null

    /** The matched string in group `i`,
     *  or `null` if nothing was matched */
    def group(i: Int): String =
      if (start(i) >= 0) source.subSequence(start(i), end(i)).toString
      else null

    /** All matched subgroups, i.e. not including group(0) */
    def subgroups: List[String] = (1 to groupCount).toList map group

    /** The char sequence before first character of match,
     *  or `null` if nothing was matched */
    def before: CharSequence =
      if (start >= 0) source.subSequence(0, start)
      else null

    /** The char sequence before first character of match in group `i`,
     *  or `null` if nothing was matched for that group  */
    def before(i: Int): CharSequence =
      if (start(i) >= 0) source.subSequence(0, start(i))
      else null

    /** Returns char sequence after last character of match,
     *  or `null` if nothing was matched */
    def after: CharSequence =
      if (end >= 0) source.subSequence(end, source.length)
      else null

    /** The char sequence after last character of match in group `i`,
     *  or `null` if nothing was matched for that group  */
    def after(i: Int): CharSequence =
      if (end(i) >= 0) source.subSequence(end(i), source.length)
      else null

    private lazy val nameToIndex: Map[String, Int] = Map[String, Int]() ++ ("" :: groupNames.toList).zipWithIndex

    /** Returns the group with given name
     *
     *  @param id The group name
     *  @return   The requested group
     *  @throws   NoSuchElementException if the requested group name is not defined
     */
    def group(id: String): String = nameToIndex.get(id) match {
      case None => throw new NoSuchElementException("group name "+id+" not defined")
      case Some(index) => group(index)
    }

    /** The matched string; equivalent to `matched.toString` */
    override def toString = matched

  }

  /** Provides information about a succesful match.
   */
  class Match(val source: CharSequence,
              private[matching] val matcher: Matcher,
              val groupNames: Seq[String]) extends MatchData {

    /** The index of the first matched character */
    val start = matcher.start

    /** The index following the last matched character */
    val end = matcher.end

    /** The number of subgroups */
    def groupCount = matcher.groupCount

    private lazy val starts: Array[Int] =
      ((0 to groupCount) map matcher.start).toArray
    private lazy val ends: Array[Int] =
      ((0 to groupCount) map matcher.end).toArray

    /** The index of the first matched character in group `i` */
    def start(i: Int) = starts(i)

    /** The index following the last matched character in group `i` */
    def end(i: Int) = ends(i)

    /** The match itself with matcher-dependent lazy vals forced,
     *  so that match is valid even once matcher is advanced
     */
    def force: this.type = { starts; ends; this }
  }

  /** An extractor object for Matches, yielding the matched string
   *
   *  This can be used to help writing replacer functions when you
   *  are not interested in match data. For example:
   *
   *  {{{
   *  import scala.util.matching.Regex.Match
   *  """\w+""".r replaceAllIn ("A simple example.", _ match { case Match(s) => s.toUpperCase })
   *  }}}
   *
   */
  object Match {
    def unapply(m: Match): Some[String] = Some(m.matched)
  }

  /** An extractor object that yields the groups in the match. Using an extractor
   *  rather than the original regex avoids recomputing the match.
   *
   *  {{{
   *  import scala.util.matching.Regex.Groups
   *
   *  val datePattern = """(\d\d\d\d)-(\d\d)-(\d\d)""".r
   *  val text = "The doc spree happened on 2011-07-15."
   *  val day = datePattern replaceAllIn(text, _ match { case Groups(year, month, day) => month+"/"+day })
   *  }}}
   */
  object Groups {
    def unapplySeq(m: Match): Option[Seq[String]] = if (m.groupCount > 0) Some(1 to m.groupCount map m.group) else None
  }

  /** A class to step through a sequence of regex matches.
   *
   *  All methods inherited from [[scala.util.matching.Regex.MatchData]] will throw
   *  a [[java.lang.IllegalStateException]] until the matcher is initialized. The
   *  matcher can be initialized by calling `hasNext` or `next()` or causing these
   *  methods to be called, such as by invoking `toString` or iterating through
   *  the iterator's elements.
   *
   *  @see [[java.util.regex.Matcher]]
   */
  class MatchIterator(val source: CharSequence, val regex: Regex, val groupNames: Seq[String])
  extends AbstractIterator[String] with Iterator[String] with MatchData { self =>

    protected[Regex] val matcher = regex.pattern.matcher(source)
    private var nextSeen = false

    /** Is there another match? */
    def hasNext: Boolean = {
      if (!nextSeen) nextSeen = matcher.find()
      nextSeen
    }

    /** The next matched substring of `source` */
    def next(): String = {
      if (!hasNext) throw new NoSuchElementException
      nextSeen = false
      matcher.group
    }

    override def toString = super[AbstractIterator].toString

    /** The index of the first matched character */
    def start: Int = matcher.start

    /** The index of the first matched character in group `i` */
    def start(i: Int): Int = matcher.start(i)

    /** The index of the last matched character */
    def end: Int = matcher.end

    /** The index following the last matched character in group `i` */
    def end(i: Int): Int = matcher.end(i)

    /** The number of subgroups */
    def groupCount = matcher.groupCount

    /** Convert to an iterator that yields MatchData elements instead of Strings */
    def matchData: Iterator[Match] = new AbstractIterator[Match] {
      def hasNext = self.hasNext
      def next = { self.next(); new Match(source, matcher, groupNames).force }
    }

    /** Convert to an iterator that yields MatchData elements instead of Strings and has replacement support */
    private[matching] def replacementData = new AbstractIterator[Match] with Replacement {
      def matcher = self.matcher
      def hasNext = self.hasNext
      def next = { self.next(); new Match(source, matcher, groupNames).force }
    }
  }

  /**
   * A trait able to build a string with replacements assuming it has a matcher.
   * Meant to be mixed in with iterators.
   */
  private[matching] trait Replacement {
    protected def matcher: Matcher

    private val sb = new java.lang.StringBuffer

    def replaced = {
      val newsb = new java.lang.StringBuffer(sb)
      matcher.appendTail(newsb)
      newsb.toString
    }

    def replace(rs: String) = matcher.appendReplacement(sb, rs)
  }

  /** Quotes strings to be used literally in regex patterns.
   *
   *  All regex metacharacters in the input match themselves literally in the output.
   *
   *  @example {{{List("US$", "CAN$").map(Regex.quote).mkString("|").r}}}
   */
  def quote(text: String): String = Pattern quote text

  /** Quotes replacement strings to be used in replacement methods.
   *
   *  Replacement methods give special meaning to backslashes (`\`) and
   *  dollar signs (`$`) in replacement strings, so they are not treated
   *  as literals. This method escapes these characters so the resulting
   *  string can be used as a literal replacement representing the input
   *  string.
   *
   *  @param text The string one wishes to use as literal replacement.
   *  @return A string that can be used to replace matches with `text`.
   *  @example {{{"CURRENCY".r.replaceAllIn(input, Regex quoteReplacement "US$")}}}
   */
  def quoteReplacement(text: String): String = Matcher quoteReplacement text
}