scala.util.matching

# Regex

#### class Regex extends Serializable

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 pattern1. 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, however, that when Regex is used as an extractor in a pattern match, 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`.

Self Type
  Regex
Annotations
  @SerialVersionUID( uid = 2094783597747625537L )
Source
  Regex.scala
Version

  1.1, 29/01/2008

Note

  ¹ A detailed description is available in java.util.regex.Pattern.

See also

  java.util.regex.Pattern

Linear Supertypes
Serializable, java.io.Serializable, AnyRef, Any
Known Subclasses
UnanchoredRegex
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1. Regex
2. Serializable
3. Serializable
4. AnyRef
5. Any

Implicitly

1. by any2stringadd
2. by any2stringfmt
3. by any2ArrowAssoc
4. by any2Ensuring

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### Instance Constructors

1. #### new Regex(regex: String, groupNames: String*)

   regex

     A string representing a regular expression

   groupNames

     A mapping from names to indices in capture groups

### Value Members

1. #### final def !=(arg0: AnyRef): Boolean

   Definition Classes
     AnyRef

2. #### final def !=(arg0: Any): Boolean

   Test two objects for inequality.

   Test two objects for inequality.

   returns

     `true` if !(this == that), false otherwise.

   Definition Classes
     Any

3. #### final def ##(): Int

   Equivalent to `x.hashCode` except for boxed numeric types and `null`.

   Equivalent to `x.hashCode` except for boxed numeric types and `null`. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For `null` returns a hashcode where `null.hashCode` throws a `NullPointerException`.

   returns

     a hash value consistent with ==

   Definition Classes
     AnyRef → Any

4. #### def +(other: String): String

   Implicit information
     This member is added by an implicit conversion from Regex to StringAdd performed by method any2stringadd in scala.Predef.
   Definition Classes
     StringAdd

5. #### def ->[B](y: B): (Regex, B)

   Implicit information
     This member is added by an implicit conversion from Regex to ArrowAssoc[Regex] performed by method any2ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()

6. #### final def ==(arg0: AnyRef): Boolean

   Definition Classes
     AnyRef

7. #### final def ==(arg0: Any): Boolean

   Test two objects for equality.

   Test two objects for equality. The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   returns

     `true` if the receiver object is equivalent to the argument; `false` otherwise.

   Definition Classes
     Any

8. #### def anchored: Regex

9. #### final def asInstanceOf[T0]: T0

   Cast the receiver object to be of type `T0`.

   Cast the receiver object to be of type `T0`.

   Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression `1.asInstanceOf[String]` will throw a `ClassCastException` at runtime, while the expression `List(1).asInstanceOf[List[String]]` will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

   returns

     the receiver object.

   Definition Classes
     Any
   Exceptions thrown
     ClassCastException

     if the receiver object is not an instance of the erasure of type `T0`.

10. #### def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the `clone` method is platform dependent.

    returns

      a copy of the receiver object.

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws()
    Note

      not specified by SLS as a member of AnyRef

11. #### def ensuring(cond: (Regex) ⇒ Boolean, msg: ⇒ Any): Regex

    Implicit information
      This member is added by an implicit conversion from Regex to Ensuring[Regex] performed by method any2Ensuring in scala.Predef.
    Definition Classes
      Ensuring

12. #### def ensuring(cond: (Regex) ⇒ Boolean): Regex

    Implicit information
      This member is added by an implicit conversion from Regex to Ensuring[Regex] performed by method any2Ensuring in scala.Predef.
    Definition Classes
      Ensuring

13. #### def ensuring(cond: Boolean, msg: ⇒ Any): Regex

    Implicit information
      This member is added by an implicit conversion from Regex to Ensuring[Regex] performed by method any2Ensuring in scala.Predef.
    Definition Classes
      Ensuring

14. #### def ensuring(cond: Boolean): Regex

    Implicit information
      This member is added by an implicit conversion from Regex to Ensuring[Regex] performed by method any2Ensuring in scala.Predef.
    Definition Classes
      Ensuring

15. #### final def eq(arg0: AnyRef): Boolean

    Tests whether the argument (`arg0`) is a reference to the receiver object (`this`).

    Tests whether the argument (`arg0`) is a reference to the receiver object (`this`).

    The `eq` method implements an equivalence relation on non-null instances of `AnyRef`, and has three additional properties:

    - It is consistent: for any non-null instances `x` and `y` of type `AnyRef`, multiple invocations of `x.eq(y)` consistently returns `true` or consistently returns `false`.
    - For any non-null instance `x` of type `AnyRef`, `x.eq(null)` and `null.eq(x)` returns `false`.
    - `null.eq(null)` returns `true`.

    When overriding the `equals` or `hashCode` methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (`o1 eq o2`), they should be equal to each other (`o1 == o2`) and they should hash to the same value (`o1.hashCode == o2.hashCode`).

    returns

      `true` if the argument is a reference to the receiver object; `false` otherwise.

    Definition Classes
      AnyRef

16. #### def equals(arg0: Any): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to `eq`.

    See also `equals` in scala.Any.

    returns

      `true` if the receiver object is equivalent to the argument; `false` otherwise.

    Definition Classes
      AnyRef → Any

17. #### def finalize(): Unit

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the `finalize` method is invoked, as well as the interaction between `finalize` and non-local returns and exceptions, are all platform dependent.

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws()
    Note

      not specified by SLS as a member of AnyRef

18. #### def findAllIn(source: CharSequence): MatchIterator

    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.

    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.

    source

      The text to match against.

    returns

      A scala.util.matching.Regex.MatchIterator of all matches.

    Example:

    1.     for (words <- """\w+""".r findAllIn "A simple example.") yield words

19. #### def findAllMatchIn(source: CharSequence): Iterator[Match]

    Return all matches of this regexp in given character sequence as a scala.collection.Iterator of scala.util.matching.Regex.Match.

    Return all matches of this regexp in given character sequence as a scala.collection.Iterator of scala.util.matching.Regex.Match.

    source

      The text to match against.

    returns

      A scala.collection.Iterator of scala.util.matching.Regex.Match for all matches.

    Example:

    1.     for (words <- """\w+""".r findAllMatchIn "A simple example.") yield words.start

20. #### def findFirstIn(source: CharSequence): Option[String]

    Return optionally first matching string of this regexp in given character sequence, or None if it does not exist.

    Return optionally first matching string of this regexp in given character sequence, or None if it does not exist.

    source

      The text to match against.

    returns

      An scala.Option of the first matching string in the text.

    Example:

    1.     """\w+""".r findFirstIn "A simple example." foreach println // prints "A"

21. #### def findFirstMatchIn(source: CharSequence): Option[Match]

    Return optionally first match of this regexp in given character sequence, or None if it does not exist.

    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.

    source

      The text to match against.

    returns

      A scala.Option of scala.util.matching.Regex.Match of the first matching string in the text.

    Example:

    1.     ("""[a-z]""".r findFirstMatchIn "A simple example.") map (_.start) // returns Some(2), the index of the first match in the text

22. #### def findPrefixMatchOf(source: CharSequence): Option[Match]

    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.

    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.

    source

      The text to match against.

    returns

      A scala.Option of the scala.util.matching.Regex.Match of the matched string.

    Example:

    1.     """\w+""".r findPrefixMatchOf "A simple example." map (_.after) // returns Some(" simple example.")

23. #### def findPrefixOf(source: CharSequence): Option[String]

    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.

    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.

    source

      The text to match against.

    returns

      A scala.Option of the matched prefix.

    Example:

    1.     """[a-z]""".r findPrefixOf "A simple example." // returns None, since the text does not begin with a lowercase letter

24. #### def formatted(fmtstr: String): String

    Returns string formatted according to given `format` string.

    Returns string formatted according to given `format` string. Format strings are as for `String.format` (@see java.lang.String.format).

    Implicit information
      This member is added by an implicit conversion from Regex to StringFormat performed by method any2stringfmt in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()

25. #### final def getClass(): Class[_]

    A representation that corresponds to the dynamic class of the receiver object.

    A representation that corresponds to the dynamic class of the receiver object.

    The nature of the representation is platform dependent.

    returns

      a representation that corresponds to the dynamic class of the receiver object.

    Definition Classes
      AnyRef → Any
    Note

      not specified by SLS as a member of AnyRef

26. #### def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

      the hash code value for this object.

    Definition Classes
      AnyRef → Any

27. #### final def isInstanceOf[T0]: Boolean

    Test whether the dynamic type of the receiver object is `T0`.

    Test whether the dynamic type of the receiver object is `T0`.

    Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression `1.isInstanceOf[String]` will return `false`, while the expression `List(1).isInstanceOf[List[String]]` will return `true`. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

    returns

      `true` if the receiver object is an instance of erasure of type `T0`; `false` otherwise.

    Definition Classes
      Any

28. #### final def ne(arg0: AnyRef): Boolean

    Equivalent to `!(this eq that)`.

    Equivalent to `!(this eq that)`.

    returns

      `true` if the argument is not a reference to the receiver object; `false` otherwise.

    Definition Classes
      AnyRef

29. #### final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
      AnyRef
    Note

      not specified by SLS as a member of AnyRef

30. #### final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
      AnyRef
    Note

      not specified by SLS as a member of AnyRef

31. #### val pattern: Pattern

    The compiled pattern

32. #### def replaceAllIn(target: CharSequence, replacer: (Match) ⇒ String): String

    Replaces all matches using a replacer function.

    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"))

    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.

    target

      The string to match.

    replacer

      The function which maps a match to another string.

    returns

      The target string after replacements.

33. #### def replaceAllIn(target: CharSequence, replacement: String): String

    Replaces all matches by a string.

    Replaces all matches by a string.

    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.

    target

      The string to match

    replacement

      The string that will replace each match

    returns

      The resulting string

    Example:

    1.     """\d+""".r replaceAllIn ("July 15", "<NUMBER>") // returns "July <NUMBER>"

34. #### def replaceFirstIn(target: CharSequence, replacement: String): String

    Replaces the first match by a string.

    Replaces the first match by a string.

    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.

    target

      The string to match

    replacement

      The string that will replace the match

    returns

      The resulting string

35. #### def replaceSomeIn(target: CharSequence, replacer: (Match) ⇒ Option[String]): String

    Replaces some of the matches using a replacer function that returns an scala.Option.

    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)

    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.

    target

      The string to match.

    replacer

      The function which optionally maps a match to another string.

    returns

      The target string after replacements.

36. #### def runMatcher(m: Matcher): Boolean

    Attributes
      protected

37. #### def split(toSplit: CharSequence): Array[String]

    Splits the provided character sequence around matches of this regexp.

    Splits the provided character sequence around matches of this regexp.

    toSplit

      The character sequence to split

    returns

      The array of strings computed by splitting the input around matches of this regexp

38. #### final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
      AnyRef

39. #### def toString(): String

    The string defining the regular expression

    The string defining the regular expression

    returns

      a String representation of the object.

    Definition Classes
      Regex → AnyRef → Any

40. #### def unanchored: UnanchoredRegex

    Create a new Regex with the same pattern, but no requirement that the entire String matches in extractor patterns.

    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"
        }

    returns

      The new unanchored regex

41. #### def unapplySeq(target: Any): Option[List[String]]

    Tries to match target (whole match) and returns the matching subgroups.

    Tries to match target (whole match) and returns the matching subgroups. if the pattern has no subgroups, then it returns an empty list on a successful match.

    Note, however, that if some subgroup has not been matched, a `null` will be returned for that subgroup.

    For example:

        val p1 = "ab*c".r
        val p2 = "a(b*)c".r

        val p1Matches = "abbbc" match {
          case p1() => true
          case _    => false
        }

        val numberOfB = "abbbc" match {
          case p2(b) => Some(b.length)
          case _     => None
        }

    target

      The string to match

    returns

      The matches

42. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws()

43. #### final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws()

44. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws()

45. #### def →[B](y: B): (Regex, B)

    Implicit information
      This member is added by an implicit conversion from Regex to ArrowAssoc[Regex] performed by method any2ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Shadowed Implict Value Members

1. #### val self: Any

   Implicit information
     This member is added by an implicit conversion from Regex to StringAdd performed by method any2stringadd in scala.Predef.
   Shadowing
     This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
     To access this member you can use a type ascription:

         (regex: StringAdd).self

   Definition Classes
     StringAdd

2. #### val self: Any

   Implicit information
     This member is added by an implicit conversion from Regex to StringFormat performed by method any2stringfmt in scala.Predef.
   Shadowing
     This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
     To access this member you can use a type ascription:

         (regex: StringFormat).self

   Definition Classes
     StringFormat

### Deprecated Value Members

1. #### def x: Regex

   Implicit information
     This member is added by an implicit conversion from Regex to ArrowAssoc[Regex] performed by method any2ArrowAssoc in scala.Predef.
   Shadowing
     This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
     To access this member you can use a type ascription:

         (regex: ArrowAssoc[Regex]).x

   Definition Classes
     ArrowAssoc
   Annotations
     @deprecated
   Deprecated

     (Since version 2.10.0) Use `leftOfArrow`instead``

2. #### def x: Regex

   Implicit information
     This member is added by an implicit conversion from Regex to Ensuring[Regex] performed by method any2Ensuring in scala.Predef.
   Shadowing
     This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
     To access this member you can use a type ascription:

         (regex: Ensuring[Regex]).x

   Definition Classes
     Ensuring
   Annotations
     @deprecated
   Deprecated

     (Since version 2.10.0) Use `resultOfEnsuring`instead``

### Inherited from Serializable

### Inherited from java.io.Serializable

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from Regex to StringAdd

### Inherited by implicit conversion any2stringfmt from Regex to StringFormat

### Inherited by implicit conversion any2ArrowAssoc from Regex to ArrowAssoc[Regex]

### Inherited by implicit conversion any2Ensuring from Regex to Ensuring[Regex]

### Ungrouped