Raised when an invalid operation is attempted on a Fiber, in particular when attempting to call/resume a dead fiber, attempting to yield from the root fiber, or calling a fiber across threads.
fiber = Fiber.new{} fiber.resume #=> nil fiber.resume #=> FiberError: dead fiber called
Raised when a feature is not implemented on the current platform. For example, methods depending on the fsync or fork system calls may raise this exception if the underlying operating system or Ruby runtime does not support them.
Note that if fork raises a NotImplementedError, then respond_to?(:fork) returns false.
A Module is a collection of methods and constants. The methods in a module may be instance methods or module methods. Instance methods appear as methods in a class when the module is included, module methods do not. Conversely, module methods may be called without creating an encapsulating object, while instance methods may not. (See Module#module_function.)
In the descriptions that follow, the parameter sym refers to a symbol, which is either a quoted string or a Symbol (such as :name).
module Mod include Math CONST = 1 def meth # ... end end Mod.class #=> Module Mod.constants #=> [:CONST, :PI, :E] Mod.instance_methods #=> [:meth]
A Regexp holds a regular expression, used to match a pattern against strings. Regexps are created using the /.../ and %r{...} literals, and by the Regexp::new constructor.
Regular expressions (regexps) 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 /pat/ and %r{pat} literals or the Regexp.new constructor.
A regexp is usually delimited with forward slashes (/). For example:
/hay/ =~ 'haystack' #=> 0 /y/.match('haystack') #=> #<MatchData "y">
If a string contains the pattern it is said to match. A literal string matches itself.
Here ‘haystack’ does not contain the pattern ‘needle’, so it doesn’t match:
/needle/.match('haystack') #=> nil
Here ‘haystack’ contains the pattern ‘hay’, so it matches:
/hay/.match('haystack') #=> #<MatchData "hay">
Specifically, /st/ requires that the string contains the letter s followed by the letter t, so it matches haystack, also.
=~ and Regexp#match Pattern matching may be achieved by using =~ operator or Regexp#match method.
=~ operator =~ is Ruby’s basic pattern-matching operator. When one operand is a regular expression and the other is a string then the regular expression is used as a pattern to match against the string. (This operator is equivalently defined by Regexp and String so the order of String and Regexp do not matter. Other classes may have different implementations of =~.) If a match is found, the operator returns index of first match in string, otherwise it returns nil.
/hay/ =~ 'haystack' #=> 0 'haystack' =~ /hay/ #=> 0 /a/ =~ 'haystack' #=> 1 /u/ =~ 'haystack' #=> nil
Using =~ operator with a String and Regexp the $~ global variable is set after a successful match. $~ holds a MatchData object. Regexp.last_match is equivalent to $~.
Regexp#match method The match method returns a MatchData object:
/st/.match('haystack') #=> #<MatchData "st">
The following are metacharacters (, ), [, ], {, }, ., ?, +, *. 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 it: \\.
/1 \+ 2 = 3\?/.match('Does 1 + 2 = 3?') #=> #<MatchData "1 + 2 = 3?"> /a\\\\b/.match('a\\\\b') #=> #<MatchData "a\\b">
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 #{...} construct.
place = "東京都" /#{place}/.match("Go to 東京都") #=> #<MatchData "東京都">
A character class is delimited with square brackets ([, ]) and lists characters that may appear at that point in the match. /[ab]/ means a or b, as opposed to /ab/ which means a followed by b.
/W[aeiou]rd/.match("Word") #=> #<MatchData "Word">
Within a character class the hyphen (-) is a metacharacter denoting an inclusive range of characters. [abcd] is equivalent to [a-d]. A range can be followed by another range, so [abcdwxyz] is equivalent to [a-dw-z]. 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 (^) 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 [a-z[0-9]] describes the same set as [a-z0-9]. However, character classes also support the && 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:
/./ - Any character except a newline.
/./m - Any character (the m modifier enables multiline mode)
/\w/ - A word character ([a-zA-Z0-9_])
/\W/ - A non-word character ([^a-zA-Z0-9_]). Please take a look at Bug #4044 if using /\W/ with the /i modifier.
/\d/ - A digit character ([0-9])
/\D/ - A non-digit character ([^0-9])
/\h/ - A hexdigit character ([0-9a-fA-F])
/\H/ - A non-hexdigit character ([^0-9a-fA-F])
/\s/ - A whitespace character: /[ \t\r\n\f\v]/
/\S/ - A non-whitespace character: /[^ \t\r\n\f\v]/
POSIX bracket expressions 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, /\d/ matches only the ASCII decimal digits (0-9); whereas /[[:digit:]]/ matches any character in the Unicode Nd category.
/[[:alnum:]]/ - Alphabetic and numeric character
/[[:alpha:]]/ - Alphabetic character
/[[:blank:]]/ - Space or tab
/[[:cntrl:]]/ - Control character
/[[:digit:]]/ - Digit
/[[:graph:]]/ - Non-blank character (excludes spaces, control characters, and similar)
/[[:lower:]]/ - Lowercase alphabetical character
/[[:print:]]/ - Like [:graph:], but includes the space character
/[[:punct:]]/ - Punctuation character
/[[:space:]]/ - Whitespace character ([:blank:], newline, carriage return, etc.)
/[[:upper:]]/ - Uppercase alphabetical
/[[:xdigit:]]/ - Digit allowed in a hexadecimal number (i.e., 0-9a-fA-F)
Ruby also supports the following non-POSIX character classes:
/[[:word:]]/ - A character in one of the following Unicode general categories Letter, Mark, Number, Connector_Punctuation
/[[:ascii:]]/ - 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">
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 quantifiers.
* - Zero or more times
+ - One or more times
? - Zero or one times (optional)
{n} - Exactly n times
{n,} - n or more times
{,m} - m or less times
{n,m} - At least n and at most m 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 greedy by default: as many occurrences as possible are matched while still allowing the overall match to succeed. By contrast, lazy matching makes the minimal amount of matches necessary for overall success. A greedy metacharacter can be made lazy by following it with ?.
Both patterns below match the string. The first 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 + matches possessively: 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.
Parentheses can be used for capturing. The text enclosed by the n<sup>th</sup> group of parentheses can be subsequently referred to with n. Within a pattern use the backreference \n; outside of the pattern use MatchData[n].
‘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 (?<name>) or (?'name') 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 \k<name>, 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 =~ operator, the captured text is also assigned to local variables with corresponding names.
/\$(?<dollars>\d+)\.(?<cents>\d+)/ =~ "$3.67" #=> 0 dollars #=> "3"
Parentheses also group the terms they enclose, allowing them to be quantified as one atomic whole.
The pattern below matches a vowel followed by 2 word characters:
/[aeiou]\w{2}/.match("Caenorhabditis elegans") #=> #<MatchData "aen">
Whereas the following pattern matches a vowel followed by a word character, twice, i.e. [aeiou]\w[aeiou]\w: ‘enor’.
/([aeiou]\w){2}/.match("Caenorhabditis elegans") #=> #<MatchData "enor" 1:"or">
The (?:…) 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 readability.
The first 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">
Grouping can be made atomic with (?>pat). This causes the subexpression pat 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 pat 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 needlessly.
The " in the pattern below matches the first character of the string, then .* matches Quote“. This causes the overall match to fail, so the text matched by .* is backtracked by one position, which leaves the final character of the string available to match "
/".*"/.match('"Quote"') #=> #<MatchData "\"Quote\"">
If .* is grouped atomically, it refuses to backtrack Quote“, even though this means that the overall match fails
/"(?>.*)"/.match('"Quote"') #=> nil
The \g<name> 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.
This pattern matches a ( character and assigns it to the paren group, tries to call that the paren sub-expression again but fails, then matches a literal ):
/\A(?<paren>\(\g<paren>*\))*\z/ =~ '()' /\A(?<paren>\(\g<paren>*\))*\z/ =~ '(())' #=> 0 # ^1 # ^2 # ^3 # ^4 # ^5 # ^6 # ^7 # ^8 # ^9 # ^10
Matches at the beginning of the string, i.e. before the first character.
Enters a named capture group called paren
Matches a literal (, the first character in the string
Calls the paren group again, i.e. recurses back to the second step
Re-enters the paren group
Matches a literal (, the second character in the string
Try to call paren a third time, but fail because doing so would prevent an overall successful match
Match a literal ), the third character in the string. Marks the end of the second recursive call
Match a literal ), the fourth character in the string
Match the end of the string
The vertical bar metacharacter (|) combines two expressions into a single one that matches either of the expressions. Each expression is an alternative.
/\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
The \p{} construct matches characters with the named property, much like POSIX bracket classes.
/\p{Alnum}/ - Alphabetic and numeric character
/\p{Alpha}/ - Alphabetic character
/\p{Blank}/ - Space or tab
/\p{Cntrl}/ - Control character
/\p{Digit}/ - Digit
/\p{Graph}/ - Non-blank character (excludes spaces, control characters, and similar)
/\p{Lower}/ - Lowercase alphabetical character
/\p{Print}/ - Like \p{Graph}, but includes the space character
/\p{Punct}/ - Punctuation character
/\p{Space}/ - Whitespace character ([:blank:], newline, carriage return, etc.)
/\p{Upper}/ - Uppercase alphabetical
/\p{XDigit}/ - Digit allowed in a hexadecimal number (i.e., 0-9a-fA-F)
/\p{Word}/ - A member of one of the following Unicode general category Letter, Mark, Number, Connector_Punctuation
/\p{ASCII}/ - A character in the ASCII character set
/\p{Any}/ - Any Unicode character (including unassigned characters)
/\p{Assigned}/ - An assigned character
A Unicode character’s General Category value can also be matched with \p{Ab} where Ab is the category’s abbreviation as described below:
/\p{L}/ - ‘Letter’
/\p{Ll}/ - ‘Letter: Lowercase’
/\p{Lm}/ - ‘Letter: Mark’
/\p{Lo}/ - ‘Letter: Other’
/\p{Lt}/ - ‘Letter: Titlecase’
/\p{Lu}/ - ‘Letter: Uppercase
/\p{Lo}/ - ‘Letter: Other’
/\p{M}/ - ‘Mark’
/\p{Mn}/ - ‘Mark: Nonspacing’
/\p{Mc}/ - ‘Mark: Spacing Combining’
/\p{Me}/ - ‘Mark: Enclosing’
/\p{N}/ - ‘Number’
/\p{Nd}/ - ‘Number: Decimal Digit’
/\p{Nl}/ - ‘Number: Letter’
/\p{No}/ - ‘Number: Other’
/\p{P}/ - ‘Punctuation’
/\p{Pc}/ - ‘Punctuation: Connector’
/\p{Pd}/ - ‘Punctuation: Dash’
/\p{Ps}/ - ‘Punctuation: Open’
/\p{Pe}/ - ‘Punctuation: Close’
/\p{Pi}/ - ‘Punctuation: Initial Quote’
/\p{Pf}/ - ‘Punctuation: Final Quote’
/\p{Po}/ - ‘Punctuation: Other’
/\p{S}/ - ‘Symbol’
/\p{Sm}/ - ‘Symbol: Math’
/\p{Sc}/ - ‘Symbol: Currency’
/\p{Sc}/ - ‘Symbol: Currency’
/\p{Sk}/ - ‘Symbol: Modifier’
/\p{So}/ - ‘Symbol: Other’
/\p{Z}/ - ‘Separator’
/\p{Zs}/ - ‘Separator: Space’
/\p{Zl}/ - ‘Separator: Line’
/\p{Zp}/ - ‘Separator: Paragraph’
/\p{C}/ - ‘Other’
/\p{Cc}/ - ‘Other: Control’
/\p{Cf}/ - ‘Other: Format’
/\p{Cn}/ - ‘Other: Not Assigned’
/\p{Co}/ - ‘Other: Private Use’
/\p{Cs}/ - ‘Other: Surrogate’
Lastly, \p{} matches a character’s Unicode script. The following scripts are supported: Arabic, Armenian, Balinese, Bengali, Bopomofo, Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic, Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana, Inherited, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao, Latin, Lepcha, Limbu, Linear_B, Lycian, Lydian, Malayalam, Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Ol_Chiki, Old_Italic, Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician, Rejang, Runic, Saurashtra, Shavian, Sinhala, Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Vai, and Yi.
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 (^).
Letter ‘A’ is not in the Unicode Ll (Letter; Lowercase) category, so this match succeeds:
/\p{^Ll}/.match("A") #=> #<MatchData "A">
Anchors are metacharacter that match the zero-width positions between characters, anchoring the match to a specific position.
^ - Matches beginning of line
$ - Matches end of line
\A - Matches beginning of string.
\Z - Matches end of string. If string ends with a newline, it matches just before newline
\z - Matches end of string
\G - Matches first matching position:
In methods like String#gsub and String#scan, it changes on each iteration. It initially matches the beginning of subject, and in each following iteration it matches where the last match finished.
" a b c".gsub(/ /, '_') #=> "____a_b_c" " a b c".gsub(/\G /, '_') #=> "____a b c"
In methods like Regexp#match and String#match that take an (optional) offset, it matches where the search begins.
"hello, world".match(/,/, 3) #=> #<MatchData ","> "hello, world".match(/\G,/, 3) #=> nil
\b - Matches word boundaries when outside brackets; backspace (0x08) when inside brackets
\B - Matches non-word boundaries
(?=pat) - Positive lookahead assertion: ensures that the following characters match pat, but doesn’t include those characters in the matched text
(?!pat) - Negative lookahead assertion: ensures that the following characters do not match pat, but doesn’t include those characters in the matched text
(?<=pat) - Positive lookbehind assertion: ensures that the preceding characters match pat, but doesn’t include those characters in the matched text
(?<!pat) - Negative lookbehind assertion: ensures that the preceding characters do not match pat, 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 tags without including the tags in the match:
/(?<=<b>)\w+(?=<\/b>)/.match("Fortune favours the <b>bold</b>") #=> #<MatchData "bold">
The end delimiter for a regexp can be followed by one or more single-letter options which control how the pattern can match.
/pat/i - Ignore case
/pat/m - Treat a newline as a character matched by .
/pat/x - Ignore whitespace and comments in the pattern
/pat/o - Perform #{} interpolation only once
i, m, and x can also be applied on the subexpression level with the (?on-off) construct, which enables options on, and disables options off for the expression enclosed by the parentheses:
/a(?i:b)c/.match('aBc') #=> #<MatchData "aBc"> /a(?-i:b)c/i.match('ABC') #=> nil
Additionally, these options can also be toggled for the remainder of the pattern:
/a(?i)bc/.match('abC') #=> #<MatchData "abC">
Options may also be used with Regexp.new:
Regexp.new("abc", Regexp::IGNORECASE) #=> /abc/i Regexp.new("abc", Regexp::MULTILINE) #=> /abc/m Regexp.new("abc # Comment", Regexp::EXTENDED) #=> /abc # Comment/x Regexp.new("abc", Regexp::IGNORECASE | Regexp::MULTILINE) #=> /abc/mi
As mentioned above, the x option enables free-spacing mode. Literal white space inside the pattern is ignored, and the octothorpe (#) character introduces a comment until the end of the line. This allows the components of the pattern to be organized 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">
There are a number of strategies for matching whitespace:
Use a pattern such as \s or \p{Space}.
Use escaped whitespace such as \ , i.e. a space preceded by a backslash.
Use a character class such as [ ].
Comments can be included in a non-x pattern with the (?#comment) construct, where comment is arbitrary text ignored by the regexp engine.
Comments in regexp literals cannot include unescaped terminator characters.
Encoding Regular expressions are assumed to use the source encoding. This can be overridden with one of the following modifiers.
/pat/u - UTF-8
/pat/e - EUC-JP
/pat/s - Windows-31J
/pat/n - 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 Encoding::CompatibilityError exception is raised.
The Regexp#fixed_encoding? predicate indicates whether the regexp has a fixed encoding, that is one incompatible with ASCII. A regexp’s encoding can be explicitly fixed by supplying Regexp::FIXEDENCODING as the second argument of Regexp.new:
r = Regexp.new("a".force_encoding("iso-8859-1"),Regexp::FIXEDENCODING) r =~ "a\u3042" # raises Encoding::CompatibilityError: incompatible encoding regexp match # (ISO-8859-1 regexp with UTF-8 string)
Pattern matching sets some global variables :
$~ is equivalent to Regexp.last_match;
$& contains the complete matched text;
$` contains string before match;
$' contains string after match;
$1, $2 and so on contain text matching first, second, etc capture group;
$+ contains last capture group.
Example:
m = /s(\w{2}).*(c)/.match('haystack') #=> #<MatchData "stac" 1:"ta" 2:"c"> $~ #=> #<MatchData "stac" 1:"ta" 2:"c"> Regexp.last_match #=> #<MatchData "stac" 1:"ta" 2:"c"> $& #=> "stac" # same as m[0] $` #=> "hay" # same as m.pre_match $' #=> "k" # same as m.post_match $1 #=> "ta" # same as m[1] $2 #=> "c" # same as m[2] $3 #=> nil # no third group in pattern $+ #=> "c" # same as m[-1]
These global variables are thread-local and method-local variables.
Certain pathological combinations of constructs can lead to abysmally bad performance.
Consider a string of 25 as, a d, 4 as, and a c.
s = 'a' * 25 + 'd' + 'a' * 4 + 'c' #=> "aaaaaaaaaaaaaaaaaaaaaaaaadaaaac"
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 #=> 26
This happens because an atom in the regexp is quantified by both an immediate + and an enclosing * with nothing to differentiate which is in control of any particular character. The nondeterminism that results produces super-linear performance. (Consult Mastering Regular Expressions (3rd ed.), pp 222, by Jeffery Friedl, 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 as against a pattern of 29 optional as followed by 29 mandatory as:
Regexp.new('a?' * 29 + 'a' * 29) =~ 'a' * 29
The 29 optional as match the string, but this prevents the 29 mandatory as 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.
The best way to improve performance is to significantly reduce the amount of backtracking needed. For this case, instead of individually matching 29 optional as, a range of optional as can be matched all at once with a{0,29}:
Regexp.new('a{0,29}' + 'a' * 29) =~ 'a' * 29
TCPServer represents a TCP/IP server socket.
A simple TCP server may look like:
require 'socket' server = TCPServer.new 2000 # Server bind to port 2000 loop do client = server.accept # Wait for a client to connect client.puts "Hello !" client.puts "Time is #{Time.now}" client.close end
A more usable server (serving multiple clients):
require 'socket' server = TCPServer.new 2000 loop do Thread.start(server.accept) do |client| client.puts "Hello !" client.puts "Time is #{Time.now}" client.close end end
UNIXServer represents a UNIX domain stream server socket.
The Vector class represents a mathematical vector, which is useful in its own right, and also constitutes a row or column of a Matrix.
Method Catalogue To create a Vector:
Vector.elements(array, copy = true)
Vector.basis(size: n, index: k)
To access elements:
To set elements:
To enumerate the elements:
Properties of vectors:
Vector arithmetic:
Vector functions:
inner_product(v), dot(v)
cross_product(v), cross(v)
Conversion to other data types:
String representations:
This class implements a pretty printing algorithm. It finds line breaks and nice indentations for grouped structure.
By default, the class assumes that primitive elements are strings and each byte in the strings have single column in width. But it can be used for other situations by giving suitable arguments for some methods:
newline object and space generation block for PrettyPrint.new
optional width argument for PrettyPrint#text
There are several candidate uses:
text formatting using proportional fonts
multibyte characters which has columns different to number of bytes
non-string formatting
Box based formatting?
Other (better) model/algorithm?
Report any bugs at bugs.ruby-lang.org
Christian Lindig, Strictly Pretty, March 2000, www.st.cs.uni-sb.de/~lindig/papers/#pretty
Philip Wadler, A prettier printer, March 1998, homepages.inf.ed.ac.uk/wadler/topics/language-design.html#prettier
Tanaka Akira <akr@fsij.org>
Resolv is a thread-aware DNS resolver library written in Ruby. Resolv can handle multiple DNS requests concurrently without blocking the entire Ruby interpreter.
See also resolv-replace.rb to replace the libc resolver with Resolv.
Resolv can look up various DNS resources using the DNS module directly.
Examples:
p Resolv.getaddress "www.ruby-lang.org" p Resolv.getname "210.251.121.214" Resolv::DNS.open do |dns| ress = dns.getresources "www.ruby-lang.org", Resolv::DNS::Resource::IN::A p ress.map(&:address) ress = dns.getresources "ruby-lang.org", Resolv::DNS::Resource::IN::MX p ress.map { |r| [r.exchange.to_s, r.preference] } end
NIS is not supported.
/etc/nsswitch.conf is not supported.
A StringIO duck-typed class that uses Tempfile instead of String as the backing store.
This is available when rubygems/test_utilities is required.
A utility class for managing temporary files. When you create a Tempfile object, it will create a temporary file with a unique filename. A Tempfile objects behaves just like a File object, and you can perform all the usual file operations on it: reading data, writing data, changing its permissions, etc. So although this class does not explicitly document all instance methods supported by File, you can in fact call any File instance method on a Tempfile object.
require 'tempfile' file = Tempfile.new('foo') file.path # => A unique filename in the OS's temp directory, # e.g.: "/tmp/foo.24722.0" # This filename contains 'foo' in its basename. file.write("hello world") file.rewind file.read # => "hello world" file.close file.unlink # deletes the temp file
When a Tempfile object is garbage collected, or when the Ruby interpreter exits, its associated temporary file is automatically deleted. This means that’s it’s unnecessary to explicitly delete a Tempfile after use, though it’s good practice to do so: not explicitly deleting unused Tempfiles can potentially leave behind large amounts of tempfiles on the filesystem until they’re garbage collected. The existence of these temp files can make it harder to determine a new Tempfile filename.
Therefore, one should always call unlink or close in an ensure block, like this:
file = Tempfile.new('foo') begin # ...do something with file... ensure file.close file.unlink # deletes the temp file end
On POSIX systems, it’s possible to unlink a file right after creating it, and before closing it. This removes the filesystem entry without closing the file handle, so it ensures that only the processes that already had the file handle open can access the file’s contents. It’s strongly recommended that you do this if you do not want any other processes to be able to read from or write to the Tempfile, and you do not need to know the Tempfile’s filename either.
For example, a practical use case for unlink-after-creation would be this: you need a large byte buffer that’s too large to comfortably fit in RAM, e.g. when you’re writing a web server and you want to buffer the client’s file upload data.
Please refer to unlink for more information and a code example.
Tempfile’s filename picking method is both thread-safe and inter-process-safe: it guarantees that no other threads or processes will pick the same filename.
Tempfile itself however may not be entirely thread-safe. If you access the same Tempfile object from multiple threads then you should protect it with a mutex.
Weak Reference class that allows a referenced object to be garbage-collected.
A WeakRef may be used exactly like the object it references.
Usage:
foo = Object.new # create a new object instance p foo.to_s # original's class foo = WeakRef.new(foo) # reassign foo with WeakRef instance p foo.to_s # should be same class GC.start # start the garbage collector p foo.to_s # should raise exception (recycled)
Threads are the Ruby implementation for a concurrent programming model.
Programs that require multiple threads of execution are a perfect candidate for Ruby’s Thread class.
For example, we can create a new thread separate from the main thread’s execution using ::new.
thr = Thread.new { puts "Whats the big deal" }
Then we are able to pause the execution of the main thread and allow our new thread to finish, using join:
thr.join #=> "Whats the big deal"
If we don’t call thr.join before the main thread terminates, then all other threads including thr will be killed.
Alternatively, you can use an array for handling multiple threads at once, like in the following example:
threads = [] threads << Thread.new { puts "Whats the big deal" } threads << Thread.new { 3.times { puts "Threads are fun!" } }
After creating a few threads we wait for them all to finish consecutively.
threads.each { |thr| thr.join }
Thread initialization In order to create new threads, Ruby provides ::new, ::start, and ::fork. A block must be provided with each of these methods, otherwise a ThreadError will be raised.
When subclassing the Thread class, the initialize method of your subclass will be ignored by ::start and ::fork. Otherwise, be sure to call super in your initialize method.
Thread termination For terminating threads, Ruby provides a variety of ways to do this.
The class method ::kill, is meant to exit a given thread:
thr = Thread.new { ... }
Thread.kill(thr) # sends exit() to thr
Alternatively, you can use the instance method exit, or any of its aliases kill or terminate.
thr.exit
Thread status Ruby provides a few instance methods for querying the state of a given thread. To get a string with the current thread’s state use status
thr = Thread.new { sleep } thr.status # => "sleep" thr.exit thr.status # => false
You can also use alive? to tell if the thread is running or sleeping, and stop? if the thread is dead or sleeping.
Thread variables and scope Since threads are created with blocks, the same rules apply to other Ruby blocks for variable scope. Any local variables created within this block are accessible to only this thread.
Each fiber has its own bucket for Thread#[] storage. When you set a new fiber-local it is only accessible within this Fiber. To illustrate:
Thread.new { Thread.current[:foo] = "bar" Fiber.new { p Thread.current[:foo] # => nil }.resume }.join
This example uses [] for getting and []= for setting fiber-locals, you can also use keys to list the fiber-locals for a given thread and key? to check if a fiber-local exists.
When it comes to thread-locals, they are accessible within the entire scope of the thread. Given the following example:
Thread.new{ Thread.current.thread_variable_set(:foo, 1) p Thread.current.thread_variable_get(:foo) # => 1 Fiber.new{ Thread.current.thread_variable_set(:foo, 2) p Thread.current.thread_variable_get(:foo) # => 2 }.resume p Thread.current.thread_variable_get(:foo) # => 2 }.join
You can see that the thread-local :foo carried over into the fiber and was changed to 2 by the end of the thread.
This example makes use of thread_variable_set to create new thread-locals, and thread_variable_get to reference them.
There is also thread_variables to list all thread-locals, and thread_variable? to check if a given thread-local exists.
Exception handling Any thread can raise an exception using the raise instance method, which operates similarly to Kernel#raise.
However, it’s important to note that an exception that occurs in any thread except the main thread depends on abort_on_exception. This option is false by default, meaning that any unhandled exception will cause the thread to terminate silently when waited on by either join or value. You can change this default by either abort_on_exception= true or setting $DEBUG to true.
With the addition of the class method ::handle_interrupt, you can now handle exceptions asynchronously with threads.
Ruby provides a few ways to support scheduling threads in your program.
The first way is by using the class method ::stop, to put the current running thread to sleep and schedule the execution of another thread.
Once a thread is asleep, you can use the instance method wakeup to mark your thread as eligible for scheduling.
You can also try ::pass, which attempts to pass execution to another thread but is dependent on the OS whether a running thread will switch or not. The same goes for priority, which lets you hint to the thread scheduler which threads you want to take precedence when passing execution. This method is also dependent on the OS and may be ignored on some platforms.
Raised when given an invalid regexp expression.
Regexp.new("?")
raises the exception:
RegexpError: target of repeat operator is not specified: /?/
ThreadGroup provides a means of keeping track of a number of threads as a group.
A given Thread object can only belong to one ThreadGroup at a time; adding a thread to a new group will remove it from any previous group.
Newly created threads belong to the same group as the thread from which they were created.
Raised when an invalid operation is attempted on a thread.
For example, when no other thread has been started:
Thread.stop
This will raises the following exception:
ThreadError: stopping only thread note: use sleep to stop forever
Solves a*x = b for x, using LU decomposition.
The Readline module provides interface for GNU Readline. This module defines a number of methods to facilitate completion and accesses input history from the Ruby interpreter. This module supported Edit Line(libedit) too. libedit is compatible with GNU Readline.
Reads one inputted line with line edit by Readline.readline method. At this time, the facilitatation completion and the key bind like Emacs can be operated like GNU Readline.
require "readline" while buf = Readline.readline("> ", true) p buf end
The content that the user input can be recorded to the history. The history can be accessed by Readline::HISTORY constant.
require "readline" while buf = Readline.readline("> ", true) p Readline::HISTORY.to_a print("-> ", buf, "\n") end
Documented by Kouji Takao <kouji dot takao at gmail dot com>.
Calculates the set of unambiguous abbreviations for a given set of strings.
require 'abbrev' require 'pp' pp Abbrev.abbrev(['ruby']) #=> {"ruby"=>"ruby", "rub"=>"ruby", "ru"=>"ruby", "r"=>"ruby"} pp Abbrev.abbrev(%w{ ruby rules })
Generates:
{ "ruby" => "ruby",
"rub" => "ruby",
"rules" => "rules",
"rule" => "rules",
"rul" => "rules" }
It also provides an array core extension, Array#abbrev.
pp %w{ summer winter }.abbrev
Generates:
{ "summer" => "summer",
"summe" => "summer",
"summ" => "summer",
"sum" => "summer",
"su" => "summer",
"s" => "summer",
"winter" => "winter",
"winte" => "winter",
"wint" => "winter",
"win" => "winter",
"wi" => "winter",
"w" => "winter" }
RubyGems is the Ruby standard for publishing and managing third party libraries.
For user documentation, see:
gem help and gem help [command]
For gem developer documentation see:
Gem::Version for version dependency notes
Further RubyGems documentation can be found at:
RubyGems API (also available from gem server)
As of RubyGems 1.3.2, RubyGems will load plugins installed in gems or $LOAD_PATH. Plugins must be named ‘rubygems_plugin’ (.rb, .so, etc) and placed at the root of your gem’s require_path. Plugins are discovered via Gem::find_files and then loaded.
For an example plugin, see the Graph gem which adds a ‘gem graph` command.
RubyGems defaults are stored in lib/rubygems/defaults.rb. If you’re packaging RubyGems or implementing Ruby you can change RubyGems’ defaults.
For RubyGems packagers, provide lib/rubygems/defaults/operating_system.rb and override any defaults from lib/rubygems/defaults.rb.
For Ruby implementers, provide lib/rubygems/defaults/#{RUBY_ENGINE}.rb and override any defaults from lib/rubygems/defaults.rb.
If you need RubyGems to perform extra work on install or uninstall, your defaults override file can set pre/post install and uninstall hooks. See Gem::pre_install, Gem::pre_uninstall, Gem::post_install, Gem::post_uninstall.
You can submit bugs to the RubyGems bug tracker on GitHub
RubyGems is currently maintained by Eric Hodel.
RubyGems was originally developed at RubyConf 2003 by:
Rich Kilmer – rich(at)infoether.com
Chad Fowler – chad(at)chadfowler.com
David Black – dblack(at)wobblini.net
Paul Brannan – paul(at)atdesk.com
Jim Weirich – jim(at)weirichhouse.org
Contributors:
Gavin Sinclair – gsinclair(at)soyabean.com.au
George Marrows – george.marrows(at)ntlworld.com
Dick Davies – rasputnik(at)hellooperator.net
Mauricio Fernandez – batsman.geo(at)yahoo.com
Simon Strandgaard – neoneye(at)adslhome.dk
Dave Glasser – glasser(at)mit.edu
Paul Duncan – pabs(at)pablotron.org
Ville Aine – vaine(at)cs.helsinki.fi
Eric Hodel – drbrain(at)segment7.net
Daniel Berger – djberg96(at)gmail.com
Phil Hagelberg – technomancy(at)gmail.com
Ryan Davis – ryand-ruby(at)zenspider.com
Evan Phoenix – evan(at)fallingsnow.net
Steve Klabnik – steve(at)steveklabnik.com
(If your name is missing, PLEASE let us know!)
See LICENSE.txt for permissions.
Thanks!
-The RubyGems Team
mkmf.rb is used by Ruby C extensions to generate a Makefile which will correctly compile and link the C extension to Ruby and a third-party library.