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authornaruse <naruse@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2009-09-17 00:40:49 +0000
committernaruse <naruse@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2009-09-17 00:40:49 +0000
commit63c7ca40d8320a5b4ecb373de69d65db49bc1122 (patch)
treec4fb9f4b08172b674685029da8b802d19d31d10e
parent6023a79deb6a9833542ee1a15666a0589b05fa1c (diff)
* doc/re.rb: New document for Ruby's fork of Oniguruma.
written by Run Paint Run Run [ruby-core:25420] * re.c: import document in doc/re.rb. * .document: add doc/re.rb. git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@24973 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
-rw-r--r--.document2
-rw-r--r--ChangeLog9
-rw-r--r--doc/re.rb584
-rw-r--r--re.c3
4 files changed, 598 insertions, 0 deletions
diff --git a/.document b/.document
index 230c50e3874..b41b4d08b0b 100644
--- a/.document
+++ b/.document
@@ -14,3 +14,5 @@ lib
# and some of the ext/ directory (which has its own .document file)
ext
+
+doc/re.rb
diff --git a/ChangeLog b/ChangeLog
index ac99774780e..59eb5a71503 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Thu Sep 17 09:37:28 2009 NARUSE, Yui <naruse@ruby-lang.org>
+
+ * doc/re.rb: New document for Ruby's fork of Oniguruma.
+ written by Run Paint Run Run [ruby-core:25420]
+
+ * re.c: import document in doc/re.rb.
+
+ * .document: add doc/re.rb.
+
Thu Sep 17 06:03:40 2009 Marc-Andre Lafortune <ruby-core@marc-andre.ca>
* lib/matrix.rb (Matrix#rank): Two bug fixes. One made
diff --git a/doc/re.rb b/doc/re.rb
new file mode 100644
index 00000000000..6eabbb5c5a4
--- /dev/null
+++ b/doc/re.rb
@@ -0,0 +1,584 @@
+module Doc
+# Regular expressions (<i>regexp</i>s) are patterns which describe the
+# contents of a string. They're used for testing whether a string contains a
+# given pattern, or extracting the portions that match. They are created
+# with the <tt>/</tt><i>pat</i><tt>/</tt> and
+# <tt>%r{</tt><i>pat</i><tt>}</tt> literals or the <tt>Regexp.new</tt>
+# constructor.
+#
+# A regexp is usually delimited with forward slashes (<tt>/</tt>). For
+# example:
+#
+# /hay/ =~ 'haystack' #=> 0
+# /y/.match('haystack') #=> #<MatchData "y">
+#
+# If a string contains the pattern it is said to <i>match</i>. A literal
+# string matches itself.
+#
+# # 'haystack' does not contain the pattern 'needle', so doesn't match.
+# /needle/.match('haystack') #=> nil
+# # 'haystack' does contain the pattern 'hay', so it matches
+# /hay/.match('haystack') #=> #<MatchData "hay">
+#
+# Specifically, <tt>/st/</tt> requires that the string contains the letter
+# _s_ followed by the letter _t_, so it matches _haystack_, also.
+#
+# == Metacharacters and Escapes
+#
+# The following are <i>metacharacters</i> <tt>(</tt>, <tt>)</tt>,
+# <tt>[</tt>, <tt>]</tt>, <tt>{</tt>, <tt>}</tt>, <tt>.</tt>, <tt>?</tt>,
+# <tt>+</tt>, <tt>*</tt>. They have a specific meaning when appearing in a
+# pattern. To match them literally they must be backslash-escaped. To match
+# a backslash literally backslash-escape that: <tt>\\\\\\</tt>.
+#
+# /1 \+ 2 = 3\?/.match('Does 1 + 2 = 3?') #=> #<MatchData "1 + 2 = 3?">
+#
+# Patterns behave like double-quoted strings so can contain the same
+# backslash escapes.
+#
+# /\s\u{6771 4eac 90fd}/.match("Go to 東京都")
+# #=> #<MatchData " 東京都">
+#
+# Arbitrary Ruby expressions can be embedded into patterns with the
+# <tt>#{...}</tt> construct.
+#
+# place = "東京都"
+# /#{place}/.match("Go to 東京都")
+# #=> #<MatchData "東京都">
+#
+# == Character Classes
+#
+# A <i>character class</i> is delimited with square brackets (<tt>[</tt>,
+# <tt>]</tt>) and lists characters that may appear at that point in the
+# match. <tt>/[ab]/</tt> means _a_ or _b_, as opposed to <tt>/ab/</tt> which
+# means _a_ followed by _b_.
+#
+# /W[aeiou]rd/.match("Word") #=> #<MatchData "Word">
+#
+# Within a character class the hyphen (<tt>-</tt>) is a metacharacter
+# denoting an inclusive range of characters. <tt>[abcd]</tt> is equivalent
+# to <tt>[a-d]</tt>. A range can be followed by another range, so
+# <tt>[abcdwxyz]</tt> is equivalent to <tt>[a-dw-z]</tt>. The order in which
+# ranges or individual characters appear inside a character class is
+# irrelevant.
+#
+# /[0-9a-f]/.match('9f') #=> #<MatchData "9">
+# /[9f]/.match('9f') #=> #<MatchData "9">
+#
+# If the first character of a character class is a caret (<tt>^</tt>) the
+# class is inverted: it matches any character _except_ those named.
+#
+# /[^a-eg-z]/.match('f') #=> #<MatchData "f">
+#
+# A character class may contain another character class. By itself this
+# isn't useful because <tt>[a-z[0-9]]</tt> describes the same set as
+# <tt>[a-z0-9]</tt>. However, character classes also support the <tt>&&</tt>
+# operator which performs set intersection on its arguments. The two can be
+# combined as follows:
+#
+# /[a-w&&[^c-g]z]/ # ([a-w] AND ([^c-g] OR z))
+# # This is equivalent to:
+# /[abh-w]/
+#
+# The following metacharacters also behave like character classes:
+#
+# * <tt>/./</tt> - Any character except a newline.
+# * <tt>/./m</tt> - Any character (the +m+ modifier enables multiline mode)
+# * <tt>/\w/</tt> - A word character (<tt>[a-zA-Z0-9_]</tt>)
+# * <tt>/\W/</tt> - A non-word character (<tt>[^a-zA-Z0-9_]</tt>)
+# * <tt>/\d/</tt> - A digit character (<tt>[0-9]</tt>)
+# * <tt>/\D/</tt> - A non-digit character (<tt>[^0-9]</tt>)
+# * <tt>/\h/</tt> - A hexdigit character (<tt>[0-9a-fA-F]</tt>)
+# * <tt>/\H/</tt> - A non-hexdigit character (<tt>[^0-9a-fA-F]</tt>)
+# * <tt>/\s/</tt> - A whitespace character: <tt>/[ \t\r\n\f]/</tt>
+# * <tt>/\S/</tt> - A non-whitespace character: <tt>/[^ \t\r\n\f]/</tt>
+#
+# POSIX <i>bracket expressions</i> are also similar to character classes.
+# They provide a portable alternative to the above, with the added benefit
+# that they encompass non-ASCII characters. For instance, <tt>/\d/</tt>
+# matches only the ASCII decimal digits (0-9); whereas <tt>/[[:digit:]]/</tt>
+# matches any character in the Unicode _Nd_ category.
+#
+# * <tt>/[[:alnum:]]/</tt> - Alphabetic and numeric character
+# * <tt>/[[:alpha:]]/</tt> - Alphabetic character
+# * <tt>/[[:blank:]]/</tt> - Space or tab
+# * <tt>/[[:cntrl:]]/</tt> - Control character
+# * <tt>/[[:digit:]]/</tt> - Digit
+# * <tt>/[[:graph:]]/</tt> - Non-blank character (excludes spaces, control
+# characters, and similar)
+# * <tt>/[[:lower:]]/</tt> - Lowercase alphabetical character
+# * <tt>/[[:print:]]/</tt> - Like [:graph:], but includes the space character
+# * <tt>/[[:punct:]]/</tt> - Punctuation character
+# * <tt>/[[:space:]]/</tt> - Whitespace character (<tt>[:blank:]</tt>, newline,
+# carriage return, etc.)
+# * <tt>/[[:upper:]]/</tt> - Uppercase alphabetical
+# * <tt>/[[:xdigit:]]/</tt> - Digit allowed in a hexadecimal number (i.e.,
+# 0-9a-fA-F)
+#
+# Ruby also supports the following non-POSIX character classes:
+#
+# * <tt>/[[:word:]]/</tt> - A character in one of the following Unicode
+# general categories _Letter_, _Mark_, _Number_,
+# <i>Connector_Punctuation<i/i>
+# * <tt>/[[:ascii:]]/</tt> - A character in the ASCII character set
+#
+# # U+06F2 is "EXTENDED ARABIC-INDIC DIGIT TWO"
+# /[[:digit:]]/.match("\u06F2") #=> #<MatchData "\u{06F2}">
+# /[[:upper:]][[:lower:]]/.match("Hello") #=> #<MatchData "He">
+# /[[:xdigit:]][[:xdigit:]]/.match("A6") #=> #<MatchData "A6">
+#
+# == Repetition
+#
+# The constructs described so far match a single character. They can be
+# followed by a repetition metacharacter to specify how many times they need
+# to occur. Such metacharacters are called <i>quantifiers</i>.
+#
+# * <tt>*</tt> - Zero or more times
+# * <tt>+</tt> - One or more times
+# * <tt>?</tt> - Zero or one times (optional)
+# * <tt>{</tt><i>n</i><tt>}</tt> - Exactly <i>n</i> times
+# * <tt>{</tt><i>n</i><tt>,}</tt> - <i>n</i> or more times
+# * <tt>{,</tt><i>m</i><tt>}</tt> - <i>m</i> or less times
+# * <tt>{</tt><i>n</i><tt>,</tt><i>m</i><tt>}</tt> - At least <i>n</i> and
+# at most <i>m</i> times
+#
+# # At least one uppercase character ('H'), at least one lowercase
+# # character ('e'), two 'l' characters, then one 'o'
+# "Hello".match(/[[:upper:]]+[[:lower:]]+l{2}o/) #=> #<MatchData "Hello">
+#
+# Repetition is <i>greedy</i> by default: as many occurrences as possible
+# are matched while still allowing the overall match to succeed. By
+# contrast, <i>lazy</i> matching makes the minimal amount of matches
+# necessary for overall success. A greedy metacharacter can be made lazy by
+# following it with <tt>?</tt>.
+#
+# # Both patterns below match the string. The fist uses a greedy
+# # quantifier so '.+' matches '<a><b>'; the second uses a lazy
+# # quantifier so '.+?' matches '<a>'.
+# /<.+>/.match("<a><b>") #=> #<MatchData "<a><b>">
+# /<.+?>/.match("<a><b>") #=> #<MatchData "<a>">
+#
+# A quantifier followed by <tt>+</tt> matches <i>possessively</i>: once it
+# has matched it does not backtrack. They behave like greedy quantifiers,
+# but having matched they refuse to "give up" their match even if this
+# jeopardises the overall match.
+#
+# == Capturing
+#
+# Parentheses can be used for <i>capturing</i>. The text enclosed by the
+# <i>n</i><sup>th</sup> group of parentheses can be subsequently referred to
+# with <i>n</i>. Within a pattern use the <i>backreference</i>
+# <tt>\</tt><i>n</i>; outside of the pattern use
+# <tt>MatchData[</tt><i>n</i><tt>]</tt>.
+#
+# # 'at' is captured by the first group of parentheses, then referred to
+# # later with \1
+# /[csh](..) [csh]\1 in/.match("The cat sat in the hat")
+# #=> #<MatchData "cat sat in" 1:"at">
+# # Regexp#match returns a MatchData object which makes the captured
+# # text available with its #[] method.
+# /[csh](..) [csh]\1 in/.match("The cat sat in the hat")[1] #=> 'at'
+#
+# Capture groups can be referred to by name when defined with the
+# <tt>(?<</tt><i>name</i><tt>>)</tt> or <tt>(?'</tt><i>name</i><tt>')</tt>
+# constructs.
+#
+# /\$(?<dollars>\d+)\.(?<cents>\d+)/.match("$3.67")
+# => #<MatchData "$3.67" dollars:"3" cents:"67">
+# /\$(?<dollars>\d+)\.(?<cents>\d+)/.match("$3.67")[:dollars] #=> "3"
+#
+# Named groups can be backreferenced with <tt>\k<</tt><i>name</i><tt>></tt>,
+# where _name_ is the group name.
+#
+# /(?<vowel>[aeiou]).\k<vowel>.\k<vowel>/.match('ototomy')
+# #=> #<MatchData "ototo" vowel:"o">
+#
+# *Note*: A regexp can't use named backreferences and numbered
+# backreferences simultaneously.
+#
+# When named capture groups are used with a literal regexp on the left-hand
+# side of an expression and the <tt>=~</tt> operator, the captured text is
+# also assigned to local variables with corresponding names.
+#
+# /\$(?<dollars>\d+)\.(?<cents>\d+)/ =~ "$3.67" #=> 0
+# dollars #=> "3"
+#
+# == Grouping
+#
+# Parentheses also <i>group</i> the terms they enclose, allowing them to be
+# quantified as one <i>atomic</i> whole.
+#
+# # The pattern below matches a vowel followed by 2 word characters:
+# # 'aen'
+# /[aeiou]\w{2}/.match("Caenorhabditis elegans") #=> #<MatchData "aen">
+# # Whereas the following pattern matches a vowel followed by a word
+# # character, twice, i.e. <tt>[aeiou]\w[aeiou]\w</tt>: 'enor'.
+# /([aeiou]\w){2}/.match("Caenorhabditis elegans")
+# #=> #<MatchData "enor" 1:"or">
+#
+# The <tt>(?:</tt>...<tt>)</tt> construct provides grouping without
+# capturing. That is, it combines the terms it contains into an atomic whole
+# without creating a backreference. This benefits performance at the slight
+# expense of readabilty.
+#
+# # The group of parentheses captures 'n' and the second 'ti'. The
+# # second group is referred to later with the backreference \2
+# /I(n)ves(ti)ga\2ons/.match("Investigations")
+# #=> #<MatchData "Investigations" 1:"n" 2:"ti">
+# # The first group of parentheses is now made non-capturing with '?:',
+# # so it still matches 'n', but doesn't create the backreference. Thus,
+# # the backreference \1 now refers to 'ti'.
+# /I(?:n)ves(ti)ga\1ons/.match("Investigations")
+# #=> #<MatchData "Investigations" 1:"ti">
+#
+# === Atomic Grouping
+#
+# Grouping can be made <i>atomic</i> with
+# <tt>(?></tt><i>pat</i><tt>)</tt>. This causes the subexpression <i>pat</i>
+# to be matched independently of the rest of the expression such that what
+# it matches becomes fixed for the remainder of the match, unless the entire
+# subexpression must be abandoned and subsequently revisited. In this
+# way <i>pat</i> is treated as a non-divisible whole. Atomic grouping is
+# typically used to optimise patterns so as to prevent the regular
+# expression engine from backtracking needlesly.
+#
+# # The <tt>"</tt> in the pattern below matches the first character of
+# # the string, then <tt>.*</tt> matches <i>Quote"</i>. This causes the
+# # overall match to fail, so the text matched by <tt>.*</tt> is
+# # backtracked by one position, which leaves the final character of the
+# # string available to match <tt>"</tt>
+# /".*"/.match('"Quote"') #=> #<MatchData "\"Quote\"">
+# # If <tt>.*</tt> is grouped atomically, it refuses to backtrack
+# # <i>Quote"</i>, even though this means that the overall match fails
+# /"(?>.*)"/.match('"Quote"') #=> nil
+#
+# == Subexpression Calls
+#
+# The <tt>\g<</tt><i>name</i><tt>></tt> syntax matches the previous
+# subexpression named _name_, which can be a group name or number, again.
+# This differs from backreferences in that it re-executes the group rather
+# than simply trying to re-match the same text.
+#
+# # Matches a <i>(</i> character and assigns it to the <tt>paren</tt>
+# # group, tries to call that the <tt>paren</tt> sub-expression again
+# # but fails, then matches a literal <i>)</i>.
+# /\A(?<paren>\(\g<paren>*\))*\z/ =~ '()'
+#
+#
+# /\A(?<paren>\(\g<paren>*\))*\z/ =~ '(())' #=> 0
+# # ^1
+# # ^2
+# # ^3
+# # ^4
+# # ^5
+# # ^6
+# # ^7
+# # ^8
+# # ^9
+# # ^10
+#
+# 1. Matches at the beginning of the string, i.e. before the first
+# character.
+# 2. Enters a named capture group called <tt>paren</tt>
+# 3. Matches a literal <i>(</i>, the first character in the string
+# 4. Calls the <tt>paren</tt> group again, i.e. recurses back to the
+# second step
+# 5. Re-enters the <tt>paren</tt> group
+# 6. Matches a literal <i>(</i>, the second character in the
+# string
+# 7. Try to call <tt>paren</tt> a third time, but fail because
+# doing so would prevent an overall successful match
+# 8. Match a literal <i>)</i>, the third character in the string.
+# Marks the end of the second recursive call
+# 9. Match a literal <i>)</i>, the fourth character in the string
+# 10. Match the end of the string
+#
+# == Alternation
+#
+# The vertical bar metacharacter (<tt>|</tt>) combines two expressions into
+# a single one that matches either of the expressions. Each expression is an
+# <i>alternative</i>.
+#
+# /\w(and|or)\w/.match("Feliformia") #=> #<MatchData "form" 1:"or">
+# /\w(and|or)\w/.match("furandi") #=> #<MatchData "randi" 1:"and">
+# /\w(and|or)\w/.match("dissemblance") #=> nil
+#
+# == Character Properties
+#
+# The <tt>\p{}</tt> construct matches characters with the named property,
+# much like POSIX bracket classes.
+#
+# * <tt>/\p{Alnum}/</tt> - Alphabetic and numeric character
+# * <tt>/\p{Alpha}/</tt> - Alphabetic character
+# * <tt>/\p{Blank}/</tt> - Space or tab
+# * <tt>/\p{Cntrl}/</tt> - Control character
+# * <tt>/\p{Digit}/</tt> - Digit
+# * <tt>/\p{Graph}/</tt> - Non-blank character (excludes spaces, control
+# characters, and similar)
+# * <tt>/\p{Lower}/</tt> - Lowercase alphabetical character
+# * <tt>/\p{Print}/</tt> - Like <tt>\p{Graph}</tt>, but includes the space character
+# * <tt>/\p{Punct}/</tt> - Punctuation character
+# * <tt>/\p{Space}/</tt> - Whitespace character (<tt>[:blank:]</tt>, newline,
+# carriage return, etc.)
+# * <tt>/\p{Upper}/</tt> - Uppercase alphabetical
+# * <tt>/\p{XDigit}/</tt> - Digit allowed in a hexadecimal number (i.e., 0-9a-fA-F)
+# * <tt>/\p{Word}/</tt> - A member of one of the following Unicode general
+# category <i>Letter</i>, <i>Mark</i>, <i>Number</i>,
+# <i>Connector\_Punctuation</i>
+# * <tt>/\p{ASCII}/</tt> - A character in the ASCII character set
+# * <tt>/\p{Any}/</tt> - Any Unicode character (including unassigned
+# characters)
+# * <tt>/\p{Assigned}/</tt> - An assigned character
+#
+# A Unicode character's <i>General Category</i> value can also be matched
+# with <tt>\p{</tt><i>Ab</i><tt>}</tt> where <i>Ab</i> is the category's
+# abbreviation as described below:
+#
+# * <tt>/\p{L}/</tt> - 'Letter'
+# * <tt>/\p{Ll}/</tt> - 'Letter: Lowercase'
+# * <tt>/\p{Lm}/</tt> - 'Letter: Mark'
+# * <tt>/\p{Lo}/</tt> - 'Letter: Other'
+# * <tt>/\p{Lt}/</tt> - 'Letter: Titlecase'
+# * <tt>/\p{Lu}/</tt> - 'Letter: Uppercase
+# * <tt>/\p{Lo}/</tt> - 'Letter: Other'
+# * <tt>/\p{M}/</tt> - 'Mark'
+# * <tt>/\p{Mn}/</tt> - 'Mark: Nonspacing'
+# * <tt>/\p{Mc}/</tt> - 'Mark: Spacing Combining'
+# * <tt>/\p{Me}/</tt> - 'Mark: Enclosing'
+# * <tt>/\p{N}/</tt> - 'Number'
+# * <tt>/\p{Nd}/</tt> - 'Number: Decimal Digit'
+# * <tt>/\p{Nl}/</tt> - 'Number: Letter'
+# * <tt>/\p{No}/</tt> - 'Number: Other'
+# * <tt>/\p{P}/</tt> - 'Punctuation'
+# * <tt>/\p{Pc}/</tt> - 'Punctuation: Connector'
+# * <tt>/\p{Pd}/</tt> - 'Punctuation: Dash'
+# * <tt>/\p{Ps}/</tt> - 'Punctuation: Open'
+# * <tt>/\p{Pe}/</tt> - 'Punctuation: Close'
+# * <tt>/\p{Pi}/</tt> - 'Punctuation: Initial Quote'
+# * <tt>/\p{Pf}/</tt> - 'Punctuation: Final Quote'
+# * <tt>/\p{Po}/</tt> - 'Punctuation: Other'
+# * <tt>/\p{S}/</tt> - 'Symbol'
+# * <tt>/\p{Sm}/</tt> - 'Symbol: Math'
+# * <tt>/\p{Sc}/</tt> - 'Symbol: Currency'
+# * <tt>/\p{Sc}/</tt> - 'Symbol: Currency'
+# * <tt>/\p{Sk}/</tt> - 'Symbol: Modifier'
+# * <tt>/\p{So}/</tt> - 'Symbol: Other'
+# * <tt>/\p{Z}/</tt> - 'Separator'
+# * <tt>/\p{Zs}/</tt> - 'Separator: Space'
+# * <tt>/\p{Zl}/</tt> - 'Separator: Line'
+# * <tt>/\p{Zp}/</tt> - 'Separator: Paragraph'
+# * <tt>/\p{C}/</tt> - 'Other'
+# * <tt>/\p{Cc}/</tt> - 'Other: Control'
+# * <tt>/\p{Cf}/</tt> - 'Other: Format'
+# * <tt>/\p{Cn}/</tt> - 'Other: Not Assigned'
+# * <tt>/\p{Co}/</tt> - 'Other: Private Use'
+# * <tt>/\p{Cs}/</tt> - 'Other: Surrogate'
+#
+# Lastly, <tt>\p{}</tt> matches a character's Unicode <i>script</i>. The
+# following scripts are supported: <i>Arabic</i>, <i>Armenian</i>,
+# <i>Balinese</i>, <i>Bengali</i>, <i>Bopomofo</i>, <i>Braille</i>,
+# <i>Buginese</i>, <i>Buhid</i>, <i>Canadian_Aboriginal</i>, <i>Carian</i>,
+# <i>Cham</i>, <i>Cherokee</i>, <i>Common</i>, <i>Coptic</i>,
+# <i>Cuneiform</i>, <i>Cypriot</i>, <i>Cyrillic</i>, <i>Deseret</i>,
+# <i>Devanagari</i>, <i>Ethiopic</i>, <i>Georgian</i>, <i>Glagolitic</i>,
+# <i>Gothic</i>, <i>Greek</i>, <i>Gujarati</i>, <i>Gurmukhi</i>, <i>Han</i>,
+# <i>Hangul</i>, <i>Hanunoo</i>, <i>Hebrew</i>, <i>Hiragana</i>,
+# <i>Inherited</i>, <i>Kannada</i>, <i>Katakana</i>, <i>Kayah_Li</i>,
+# <i>Kharoshthi</i>, <i>Khmer</i>, <i>Lao</i>, <i>Latin</i>, <i>Lepcha</i>,
+# <i>Limbu</i>, <i>Linear_B</i>, <i>Lycian</i>, <i>Lydian</i>,
+# <i>Malayalam</i>, <i>Mongolian</i>, <i>Myanmar</i>, <i>New_Tai_Lue</i>,
+# <i>Nko</i>, <i>Ogham</i>, <i>Ol_Chiki</i>, <i>Old_Italic</i>,
+# <i>Old_Persian</i>, <i>Oriya</i>, <i>Osmanya</i>, <i>Phags_Pa</i>,
+# <i>Phoenician</i>, <i>Rejang</i>, <i>Runic</i>, <i>Saurashtra</i>,
+# <i>Shavian</i>, <i>Sinhala</i>, <i>Sundanese</i>, <i>Syloti_Nagri</i>,
+# <i>Syriac</i>, <i>Tagalog</i>, <i>Tagbanwa</i>, <i>Tai_Le</i>,
+# <i>Tamil</i>, <i>Telugu</i>, <i>Thaana</i>, <i>Thai</i>, <i>Tibetan</i>,
+# <i>Tifinagh</i>, <i>Ugaritic</i>, <i>Vai</i>, and <i>Yi</i>.
+#
+# # Unicode codepoint U+06E9 is named "ARABIC PLACE OF SAJDAH" and
+# # belongs to the Arabic script.
+# /\p{Arabic}/.match("\u06E9") #=> #<MatchData "\u06E9">
+#
+# All character properties can be inverted by prefixing their name with a
+# caret (<tt>^</tt>).
+#
+# # Letter 'A' is not in the Unicode Ll (Letter; Lowercase) category, so
+# # this match succeeds
+# /\p{^Ll}/.match("A") #=> #<MatchData "A">
+#
+# == Anchors
+#
+# Anchors are metacharacter that match the zero-width positions between
+# characters, <i>anchoring</i> the match to a specific position.
+#
+# * <tt>^</tt> - Matches beginning of line
+# * <tt>$</tt> - Matches end of line
+# * <tt>\A</tt> - Matches beginning of string.
+# * <tt>\Z</tt> - Matches end of string. If string ends with a newline,
+# it matches just before newline
+# * <tt>\z</tt> - Matches end of string
+# * <tt>\G</tt> - Matches point where last match finished
+# * <tt>\b</tt> - Matches word boundaries when outside brackets; backspace
+# (0x08) inside brackets
+# * <tt>\B</tt> - Matches non-word boundaries
+# * <tt>(?=</tt><i>pat</i><tt>)</tt> - <i>Positive lookahead</i> assertion:
+# ensures that the following characters match <i>pat</i>, but doesn't
+# include those characters in the matched text
+# * <tt>(?!</tt><i>pat</i><tt>)</tt> - <i>Negative lookahead</i> assertion:
+# ensures that the following characters do not match <i>pat</i>, but
+# doesn't include those characters in the matched text
+# * <tt>(?<=</tt><i>pat</i><tt>)</tt> - <i>Positive lookbehind</i>
+# assertion: ensures that the preceding characters match <i>pat</i>, but
+# doesn't include those characters in the matched text
+# * <tt>(?<!</tt><i>pat</i><tt>)</tt> - <i>Negative lookbehind</i>
+# assertion: ensures that the preceding characters do not match
+# <i>pat</i>, but doesn't include those characters in the matched text
+#
+# # If a pattern isn't anchored it can begin at any point in the string
+# /real/.match("surrealist") #=> #<MatchData "real">
+# # Anchoring the pattern to the beginning of the string forces the
+# # match to start there. 'real' doesn't occur at the beginning of the
+# # string, so now the match fails
+# /\Areal/.match("surrealist") #=> nil
+# # The match below fails because although 'Demand' contains 'and', the
+# pattern does not occur at a word boundary.
+# /\band/.match("Demand")
+# # Whereas in the following example 'and' has been anchored to a
+# # non-word boundary so instead of matching the first 'and' it matches
+# # from the fourth letter of 'demand' instead
+# /\Band.+/.match("Supply and demand curve") #=> #<MatchData "and curve">
+# # The pattern below uses positive lookahead and positive lookbehind to
+# # match text appearing in <b></b> tags without including the tags in the
+# # match
+# /(?<=<b>)\w+(?=<\/b>)/.match("Fortune favours the <b>bold</b>")
+# #=> #<MatchData "bold">
+#
+# == Options
+#
+# The end delimiter for a regexp can be followed by one or more single-letter
+# options which control how the pattern can match.
+#
+# * <tt>/pat/i</tt> - Ignore case
+# * <tt>/pat/m</tt> - Treat a newline as a character matched by <tt>.</tt>
+# * <tt>/pat/x</tt> - Ignore whitespace and comments in the pattern
+# * <tt>/pat/o</tt> - Perform <tt>#{}</tt> interpolation only once
+#
+# <tt>i</tt>, <tt>m</tt>, and <tt>x</tt> can also be applied on the
+# subexpression level with the
+# <tt>(?</tt><i>on</i><tt>-</tt><i>off</i><tt>)</tt> construct, which
+# enables options <i>on</i>, and disables options <i>off</i> for the
+# expression enclosed by the parentheses.
+#
+# /a(?i:b)c/.match('aBc') #=> #<MatchData "aBc">
+# /a(?i:b)c/.match('abc') #=> #<MatchData "abc">
+#
+# == Free-Spacing Mode and Comments
+#
+# As mentioned above, the <tt>x</tt> option enables <i>free-spacing</i>
+# mode. Literal white space inside the pattern is ignored, and the
+# octothorpe (<tt>#</tt>) character introduces a comment until the end of
+# the line. This allows the components of the pattern to be organised in a
+# potentially more readable fashion.
+#
+# # A contrived pattern to match a number with optional decimal places
+# float_pat = /\A
+# [[:digit:]]+ # 1 or more digits before the decimal point
+# (\. # Decimal point
+# [[:digit:]]+ # 1 or more digits after the decimal point
+# )? # The decimal point and following digits are optional
+# \Z/x
+# float_pat.match('3.14') #=> #<MatchData "3.14" 1:".14">
+#
+# *Note*: To match whitespace in an <tt>x</tt> pattern use an escape such as
+# <tt>\s</tt> or <tt>\p{Space}</tt>.
+#
+# Comments can be included in a non-<tt>x</tt> pattern with the
+# <tt>(?#</tt><i>comment</i><tt>)</tt> construct, where <i>comment</i> is
+# arbitrary text ignored by the regexp engine.
+#
+# == Encoding
+#
+# Regular expressions are assumed to use the source encoding. This can be
+# overridden with one of the following modifiers.
+#
+# * <tt>/</tt><i>pat</i><tt>/u</tt> - UTF-8
+# * <tt>/</tt><i>pat</i><tt>/e</tt> - EUC-JP
+# * <tt>/</tt><i>pat</i><tt>/s</tt> - Windows-31J
+# * <tt>/</tt><i>pat</i><tt>/n</tt> - ASCII-8BIT
+#
+# A regexp can be matched against a string when they either share an
+# encoding, or the regexp's encoding is _US-ASCII_ and the string's encoding
+# is ASCII-compatible.
+#
+# If a match between incompatible encodings is attempted an
+# <tt>Encoding::CompatibilityError</tt> exception is raised.
+#
+# The <tt>Regexp#fixed_encoding?</tt> predicate indicates whether the regexp
+# has a <i>fixed</i> encoding, that is one incompatible with ASCII. A
+# regexp's encoding can be explicitly fixed by supplying
+# <tt>Regexp::FIXEDENCODING</tt> as the second argument of
+# <tt>Regexp.new</tt>:
+#
+# r = Regexp.new("a".force_encoding("iso-8859-1"),Regexp::FIXEDENCODING)
+# r =~"a\u3042"
+# #=> Encoding::CompatibilityError: incompatible encoding regexp match
+# (ISO-8859-1 regexp with UTF-8 string)
+#
+# == Performance
+#
+# Certain pathological combinations of constructs can lead to abysmally bad
+# performance.
+#
+# Consider a string of 25 <i>a</i>s, a <i>d</i>, 4 <i>a</i>s, and a
+# <i>c</i>.
+#
+# s = 'a' * 25 + 'd' 'a' * 4 + 'c'
+# #=> "aaaaaaaaaaaaaaaaaaaaaaaaadadadadac"
+#
+# The following patterns match instantly as you would expect:
+#
+# /(b|a)/ =~ s #=> 0
+# /(b|a+)/ =~ s #=> 0
+# /(b|a+)*\/ =~ s #=> 0
+#
+# However, the following pattern takes appreciably longer:
+#
+# /(b|a+)*c/ =~ s #=> 32
+#
+# This happens because an atom in the regexp is quantified by both an
+# immediate <tt>+</tt> and an enclosing <tt>*</tt> with nothing to
+# differentiate which is in control of any particular character. The
+# nondeterminism that results produces super-linear performance. (Consult
+# <i>Mastering Regular Expressions</i> (3rd ed.), pp 222, by
+# <i>Jeffery Friedl</i>, for an in-depth analysis). This particular case
+# can be fixed by use of atomic grouping, which prevents the unnecessary
+# backtracking:
+#
+# (start = Time.now) && /(b|a+)*c/ =~ s && (Time.now - start)
+# #=> 24.702736882
+# (start = Time.now) && /(?>b|a+)*c/ =~ s && (Time.now - start)
+# #=> 0.000166571
+#
+# A similar case is typified by the following example, which takes
+# approximately 60 seconds to execute for me:
+#
+# # Match a string of 29 <i>a</i>s against a pattern of 29 optional
+# # <i>a</i>s followed by 29 mandatory <i>a</i>s.
+# Regexp.new('a?' * 29 + 'a' * 29) =~ 'a' * 29
+#
+# The 29 optional <i>a</i>s match the string, but this prevents the 29
+# mandatory <i>a</i>s that follow from matching. Ruby must then backtrack
+# repeatedly so as to satisfy as many of the optional matches as it can
+# while still matching the mandatory 29. It is plain to us that none of the
+# optional matches can succeed, but this fact unfortunately eludes Ruby.
+#
+# One approach for improving performance is to anchor the match to the
+# beginning of the string, thus significantly reducing the amount of
+# backtracking needed.
+#
+# Regexp.new('\A' 'a?' * 29 + 'a' * 29).match('a' * 29)
+# #=> #<MatchData "aaaaaaaaaaaaaaaaaaaaaaaaaaaaa">
+#
+#
+ class Regexp; end
+end
diff --git a/re.c b/re.c
index e22c8c04c29..ec20c44a3d5 100644
--- a/re.c
+++ b/re.c
@@ -3433,6 +3433,9 @@ re_warn(const char *s)
* <code>%r{...}</code> literals, and by the <code>Regexp::new</code>
* constructor.
*
+ * A comprehensive reference for regexp syntax and usage is available as
+ * +Doc::Regexp+.
+ *
*/
void