A regular expression is used to determine whether a string matches a pattern and, if it does, to extract or transform the parts that match.
Usage
This class delegates to thejava.util.regex package of the Java Platform. See the documentation forjava.util.regex.Pattern for details about the regular expression syntax for pattern strings.
An instance ofRegex represents a compiled regular expression pattern. Since compilation is expensive, frequently usedRegexes should be constructed once, outside of loops and perhaps in a companion object.
The canonical way to create aRegex is by using the methodr, provided implicitly for strings:
val date = raw"(\d{4})-(\d{2})-(\d{2})".rSince escapes are not processed in multi-line string literals, using triple quotes avoids having to escape the backslash character, so that"\\d" can be written"""\d""". The same result is achieved with certain interpolators, such asraw"\d".r or a custom interpolatorr"\d" that also compiles theRegex.
Extraction
To extract the capturing groups when aRegex is matched, use it as an extractor in a pattern match:
"2004-01-20" match { case date(year, month, day) => s"$year was a good year for PLs."}To check only whether theRegex matches, ignoring any groups, use a sequence wildcard:
"2004-01-20" match { case date(_*) => "It's a date!"}That works because aRegex extractor produces a sequence of strings. Extracting only the year from a date could also be expressed with a sequence wildcard:
"2004-01-20" match { case date(year, _*) => s"$year was a good year for PLs."}In a pattern match,Regex normally matches the entire input. However, an unanchoredRegex finds the pattern anywhere in the input.
val embeddedDate = date.unanchored"Date: 2004-01-20 17:25:18 GMT (10 years, 28 weeks, 5 days, 17 hours and 51 minutes ago)" match { case embeddedDate("2004", "01", "20") => "A Scala is born."}Find Matches
To find or replace matches of the pattern, use the various find and replace methods. For each method, there is a version for working with matched strings and another for working withMatch objects.
For example, pattern matching with an unanchoredRegex, as in the previous example, can also be accomplished usingfindFirstMatchIn. ThefindFirst methods return anOption which is non-empty if a match is found, orNone for no match:
val dates = "Important dates in history: 2004-01-20, 1958-09-05, 2010-10-06, 2011-07-15"val firstDate = date.findFirstIn(dates).getOrElse("No date found.")val firstYear = for (m <- date.findFirstMatchIn(dates)) yield m.group(1)To find all matches:
val allYears = for (m <- date.findAllMatchIn(dates)) yield m.group(1)To check whether input is matched by the regex:
date.matches("2018-03-01") // truedate.matches("Today is 2018-03-01") // falsedate.unanchored.matches("Today is 2018-03-01") // trueTo iterate over the matched strings, usefindAllIn, which returns a special iterator that can be queried for theMatchData of the last match:
val mi = date.findAllIn(dates)while (mi.hasNext) { val d = mi.next if (mi.group(1).toInt < 1960) println(s"$d: An oldie but goodie.")}Although theMatchIterator returned byfindAllIn is used like anyIterator, with alternating calls tohasNext andnext,hasNext has the additional side effect of advancing the underlying matcher to the next unconsumed match. This effect is visible in theMatchData representing the "current match".
val r = "(ab+c)".rval s = "xxxabcyyyabbczzz"r.findAllIn(s).start // 3val mi = r.findAllIn(s)mi.hasNext // truemi.start // 3mi.next() // "abc"mi.start // 3mi.hasNext // truemi.start // 9mi.next() // "abbc"The example shows that methods onMatchData such asstart will advance to the first match, if necessary. It also shows thathasNext will advance to the next unconsumed match, ifnext has already returned the current match.
The currentMatchData can be captured using thematchData method. Alternatively,findAllMatchIn returns anIterator[Match], where there is no interaction between the iterator andMatch objects it has already produced.
Note thatfindAllIn finds matches that don't overlap. (SeefindAllIn for more examples.)
val num = raw"(\d+)".rval all = num.findAllIn("123").toList // List("123"), not List("123", "23", "3")Replace Text
Text replacement can be performed unconditionally or as a function of the current match:
val redacted = date.replaceAllIn(dates, "XXXX-XX-XX")val yearsOnly = date.replaceAllIn(dates, m => m.group(1))val months = (0 to 11).map { i => val c = Calendar.getInstance; c.set(2014, i, 1); f"$c%tb" }val reformatted = date.replaceAllIn(dates, _ match { case date(y,m,d) => f"${months(m.toInt - 1)} $d, $y" })Pattern matching theMatch against theRegex that created it does not reapply theRegex. In the expression forreformatted, eachdate match is computed once. But it is possible to apply aRegex to aMatch resulting from a different pattern:
val docSpree = """2011(?:-\d{2}){2}""".rval docView = date.replaceAllIn(dates, _ match { case docSpree() => "Historic doc spree!" case _ => "Something else happened"})Value parameters
- groupNames
A mapping from names to indices in capture groups
- pattern
The compiled pattern
Attributes
- See also
- Companion
- object
- Source
- Regex.scala
- Graph
- Supertypes
- Known subtypes
- traitUnanchoredRegex
- Self type
Members list
Value members
Constructors
Compile a regular expression, supplied as a string, into a pattern that can be matched against inputs.
Compile a regular expression, supplied as a string, into a pattern that can be matched against inputs.
If group names are supplied, they can be used this way:
val namedDate = new Regex("""(\d\d\d\d)-(\d\d)-(\d\d)""", "year", "month", "day")val namedYears = for (m <- namedDate findAllMatchIn dates) yield m group "year"Inline group names are preferred over group names supplied to the constructor when retrieving matched groups by name. Group names supplied to the constructor should be considered deprecated.
This constructor does not support options as flags, which must be supplied as inline flags in the pattern string:(?idmsuxU).
Value parameters
- groupNames
Names of capturing groups.
- regex
The regular expression to compile.
Attributes
- Source
- Regex.scala
Concrete methods
Attributes
- Source
- Regex.scala
Return all non-overlapping matches of thisRegex in the given character sequence as ascala.util.matching.Regex.MatchIterator, which is a specialscala.collection.Iterator that returns the matched strings but can also be queried for more data about the last match, such as capturing groups and start position.
Return all non-overlapping matches of thisRegex in the given character sequence as ascala.util.matching.Regex.MatchIterator, which is a specialscala.collection.Iterator that returns the matched strings but can also be queried for more data about the last match, such as capturing groups and start position.
AMatchIterator can also be converted into an iterator that returns objects of typescala.util.matching.Regex.Match, such as is normally returned byfindAllMatchIn.
Where potential matches overlap, the first possible match is returned, followed by the next match that follows the input consumed by the first match:
val hat = "hat[^a]+".rval hathaway = "hathatthattthatttt"val hats = hat.findAllIn(hathaway).toList // List(hath, hattth)val pos = hat.findAllMatchIn(hathaway).map(_.start).toList // List(0, 7)To return overlapping matches, it is possible to formulate a regular expression with lookahead (?=) that does not consume the overlapping region.
val madhatter = "(h)(?=(at[^a]+))".rval madhats = madhatter.findAllMatchIn(hathaway).map { case madhatter(x,y) => s"$x$y"}.toList // List(hath, hatth, hattth, hatttt)Attempting to retrieve match information after exhausting the iterator results injava.lang.IllegalStateException. Seescala.util.matching.Regex.MatchIterator for details.
Value parameters
- source
The text to match against.
Attributes
- Returns
Ascala.util.matching.Regex.MatchIterator of matched substrings.
- Example
for (words <- """\w+""".r findAllIn "A simple example.") yield words- Source
- Regex.scala
Return all non-overlapping matches of this regexp in given character sequence as ascala.collection.Iterator ofscala.util.matching.Regex.Match.
Return all non-overlapping matches of this regexp in given character sequence as ascala.collection.Iterator ofscala.util.matching.Regex.Match.
Value parameters
- source
The text to match against.
Attributes
- Returns
Ascala.collection.Iterator ofscala.util.matching.Regex.Match for all matches.
- Example
for (words <- """\w+""".r findAllMatchIn "A simple example.") yield words.start- Source
- Regex.scala
Return an optional first matching string of thisRegex in the given character sequence, or None if there is no match.
Return an optional first matching string of thisRegex in the given character sequence, or None if there is no match.
Value parameters
- source
The text to match against.
Attributes
- Returns
Anscala.Option of the first matching string in the text.
- Example
"""\w+""".r findFirstIn "A simple example." foreach println // prints "A"- Source
- Regex.scala
Return an optional first match of thisRegex in the given character sequence, or None if it does not exist.
Return an optional first match of thisRegex in the given character sequence, or None if it does not exist.
If the match is successful, thescala.util.matching.Regex.Match can be queried for more data.
Value parameters
- source
The text to match against.
Attributes
- Returns
Ascala.Option ofscala.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- Source
- Regex.scala
Return an optional match of thisRegex at the beginning of the given character sequence, or None if it matches no prefix of the character sequence.
Return an optional match of thisRegex at the beginning of the given character sequence, or None if it matches no prefix of the character sequence.
UnlikefindFirstMatchIn, this method will only return a match at the beginning of the input.
Value parameters
- source
The text to match against.
Attributes
- Returns
Ascala.Option of thescala.util.matching.Regex.Match of the matched string.
- Example
"""\w+""".r findPrefixMatchOf "A simple example." map (_.after) // returns Some(" simple example.")- Source
- Regex.scala
Return an optional match of thisRegex at the beginning of the given character sequence, or None if it matches no prefix of the character sequence.
Return an optional match of thisRegex at the beginning of the given character sequence, or None if it matches no prefix of the character sequence.
UnlikefindFirstIn, this method will only return a match at the beginning of the input.
Value parameters
- source
The text to match against.
Attributes
- Returns
Ascala.Option of the matched prefix.
- Example
"""\p{Lower}""".r findPrefixOf "A simple example." // returns None, since the text does not begin with a lowercase letter- Source
- Regex.scala
Returns whether thisRegex matches the given character sequence.
Returns whether thisRegex matches the given character sequence.
Like the extractor, this method takes anchoring into account.
Value parameters
- source
The text to match against
Attributes
- Returns
true if and only if
sourcematches thisRegex.- See also
- Example
"""\d+""".r matches "123" // returns true- Source
- Regex.scala
Attributes
- Source
- Regex.scala
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. UseRegex.quoteReplacement to escape these characters.
Value parameters
- replacement
The string that will replace each match
- target
The string to match
Attributes
- Returns
The resulting string
- Example
"""\d+""".r replaceAllIn ("July 15", "<NUMBER>") // returns "July <NUMBER>"- Source
- Regex.scala
Replaces all matches using a replacer function.
Replaces all matches using a replacer function. The replacer function takes ascala.util.matching.Regex.Match so that extra information can be obtained from the match. For example:
import scala.util.matching.Regexval 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 => s"${m group "month"}/${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. UseRegex.quoteReplacement to escape these characters.
Value parameters
- replacer
The function which maps a match to another string.
- target
The string to match.
Attributes
- Returns
The target string after replacements.
- Source
- Regex.scala
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. UseRegex.quoteReplacement to escape these characters.
Value parameters
- replacement
The string that will replace the match
- target
The string to match
Attributes
- Returns
The resulting string
- Source
- Regex.scala
Replaces some of the matches using a replacer function that returns anscala.Option.
Replaces some of the matches using a replacer function that returns anscala.Option. The replacer function takes ascala.util.matching.Regex.Match so that extra information can be obtained from the match. For example:
import scala.util.matching.Regex._val vars = Map("x" -> "a var", "y" -> """some $ and \ signs""")val text = "A text with variables %x, %y and %z."val varPattern = """%(\w+)""".rval mapper = (m: Match) => vars 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. UseRegex.quoteReplacement to escape these characters.
Value parameters
- replacer
The function which optionally maps a match to another string.
- target
The string to match.
Attributes
- Returns
The target string after replacements.
- Source
- Regex.scala
Splits the provided character sequence around matches of this regexp.
Splits the provided character sequence around matches of this regexp.
Value parameters
- toSplit
The character sequence to split
Attributes
- Returns
The array of strings computed by splitting the input around matches of this regexp
- Source
- Regex.scala
The string defining the regular expression
Create a new Regex with the same pattern, but no requirement that the entire String matches in extractor patterns andRegex#matches.
Create a new Regex with the same pattern, but no requirement that the entire String matches in extractor patterns andRegex#matches.
Normally, matching ondate behaves as though the pattern were enclosed in anchors,"^pattern$".
The unanchoredRegex behaves as though those anchors were removed.
Note that this method does not actually strip any matchers from the pattern.
Callinganchored returns the originalRegex.
val date = """(\d\d\d\d)-(\d\d)-(\d\d)""".r.unanchoredval date(year, month, day) = "Date 2011-07-15" // OKval copyright: String = "Date of this document: 2011-07-15" match { case date(year, month, day) => s"Copyright $year" // OK case _ => "No copyright"}Attributes
- Returns
The new unanchored regex
- Source
- Regex.scala
Tries to match ajava.lang.CharSequence.
Tries to match ajava.lang.CharSequence.
If the match succeeds, the result is a list of the matching groups (or anull 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 unanchoredRegex.
For example:
val p1 = "ab*c".rval p1Matches = "abbbc" match { case p1() => true // no groups case _ => false}val p2 = "a(b*)c".rval p2Matches = "abbbc" match { case p2(_*) => true // any groups case _ => false}val numberOfB = "abbbc" match { case p2(b) => Some(b.length) // one group case _ => None}val p3 = "b*".r.unanchoredval p3Matches = "abbbc" match { case p3() => true // find the b's case _ => false}val p4 = "a(b*)(c+)".rval p4Matches = "abbbcc" match { case p4(_*) => true // multiple groups case _ => false}val allGroups = "abbbcc" match { case p4(all @ _*) => all mkString "/" // "bbb/cc" case _ => ""}val cGroup = "abbbcc" match { case p4(_, c) => c case _ => ""}Value parameters
- s
The string to match
Attributes
- Returns
The matches
- Source
- Regex.scala
Tries to match the String representation of ascala.Char.
Tries to match the String representation of ascala.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 matchval r = """(\p{Lower})""".rcat(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 extractval r = """\p{Lower}""".rcat(0) match { case r(x) => true } // no matchcat(0) match { case r(_) => true } // no matchcat(0) match { case r(_*) => true } // matchescat(0) match { case r() => true } // matches// even if there are multiple groups, only one is returnedval r = """((.))""".rcat(0) match { case r(_) => true } // matchescat(0) match { case r(_,_) => true } // no matchValue parameters
- c
The Char to match
Attributes
- Returns
The match
- Source
- Regex.scala
Tries to match on ascala.util.matching.Regex.Match.
Tries to match on ascala.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.
Attributes
- Source
- Regex.scala
Concrete fields
Attributes
- Source
- Regex.scala