PERLUNICODE
Section: Perl Programmers Reference Guide (1)Updated: 2009-05-14
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NAME
perlunicode - Unicode support in PerlDESCRIPTION
Important Caveats
Unicode support is an extensive requirement. While Perl does not implement the Unicode standard or the accompanying technical reports from cover to cover, Perl does support many Unicode features.People who want to learn to use Unicode in Perl, should probably read the Perl Unicode tutorial, perlunitut, before reading this reference document.
- Input and Output Layers
-
Perl knows when a filehandle uses Perl's internal Unicode encodings
(UTF-8, or UTF-EBCDIC if in EBCDIC) if the filehandle is opened with
the ``:utf8'' layer. Other encodings can be converted to Perl's
encoding on input or from Perl's encoding on output by use of the
``:encoding(...)'' layer. See open.
To indicate that Perl source itself is in UTF-8, use "use utf8;".
- Regular Expressions
- The regular expression compiler produces polymorphic opcodes. That is, the pattern adapts to the data and automatically switches to the Unicode character scheme when presented with data that is internally encoded in UTF-8 --- or instead uses a traditional byte scheme when presented with byte data.
- use utf8 still needed to enable UTF-8/UTF-EBCDIC in scripts
- As a compatibility measure, the "use utf8" pragma must be explicitly included to enable recognition of UTF-8 in the Perl scripts themselves (in string or regular expression literals, or in identifier names) on ASCII-based machines or to recognize UTF-EBCDIC on EBCDIC-based machines. These are the only times when an explicit "use utf8" is needed. See utf8.
- BOM-marked scripts and UTF-16 scripts autodetected
- If a Perl script begins marked with the Unicode BOM (UTF-16LE, UTF16-BE, or UTF-8), or if the script looks like non-BOM-marked UTF-16 of either endianness, Perl will correctly read in the script as Unicode. (BOMless UTF-8 cannot be effectively recognized or differentiated from ISO 8859-1 or other eight-bit encodings.)
- use encoding needed to upgrade non-Latin-1 byte strings
-
By default, there is a fundamental asymmetry in Perl's Unicode model:
implicit upgrading from byte strings to Unicode strings assumes that
they were encoded in ISO 8859-1 (Latin-1), but Unicode strings are
downgraded with UTF-8 encoding. This happens because the first 256
codepoints in Unicode happens to agree with Latin-1.
See ``Byte and Character Semantics'' for more details.
Byte and Character Semantics
Beginning with version 5.6, Perl uses logically-wide characters to represent strings internally.In future, Perl-level operations will be expected to work with characters rather than bytes.
However, as an interim compatibility measure, Perl aims to provide a safe migration path from byte semantics to character semantics for programs. For operations where Perl can unambiguously decide that the input data are characters, Perl switches to character semantics. For operations where this determination cannot be made without additional information from the user, Perl decides in favor of compatibility and chooses to use byte semantics.
Under byte semantics, when "use locale" is in effect, Perl uses the semantics associated with the current locale. Absent a "use locale", Perl currently uses US-ASCII (or Basic Latin in Unicode terminology) byte semantics, meaning that characters whose ordinal numbers are in the range 128 - 255 are undefined except for their ordinal numbers. This means that none have case (upper and lower), nor are any a member of character classes, like "[:alpha:]" or "\w". (But all do belong to the "\W" class or the Perl regular expression extension "[:^alpha:]".)
This behavior preserves compatibility with earlier versions of Perl, which allowed byte semantics in Perl operations only if none of the program's inputs were marked as being as source of Unicode character data. Such data may come from filehandles, from calls to external programs, from information provided by the system (such as %ENV), or from literals and constants in the source text.
The "bytes" pragma will always, regardless of platform, force byte semantics in a particular lexical scope. See bytes.
The "utf8" pragma is primarily a compatibility device that enables recognition of UTF-(8|EBCDIC) in literals encountered by the parser. Note that this pragma is only required while Perl defaults to byte semantics; when character semantics become the default, this pragma may become a no-op. See utf8.
Unless explicitly stated, Perl operators use character semantics for Unicode data and byte semantics for non-Unicode data. The decision to use character semantics is made transparently. If input data comes from a Unicode source---for example, if a character encoding layer is added to a filehandle or a literal Unicode string constant appears in a program---character semantics apply. Otherwise, byte semantics are in effect. The "bytes" pragma should be used to force byte semantics on Unicode data.
If strings operating under byte semantics and strings with Unicode character data are concatenated, the new string will have character semantics. This can cause surprises: See ``BUGS'', below
Under character semantics, many operations that formerly operated on bytes now operate on characters. A character in Perl is logically just a number ranging from 0 to 2**31 or so. Larger characters may encode into longer sequences of bytes internally, but this internal detail is mostly hidden for Perl code. See perluniintro for more.
Effects of Character Semantics
Character semantics have the following effects:- *
-
Strings---including hash keys---and regular expression patterns may
contain characters that have an ordinal value larger than 255.
If you use a Unicode editor to edit your program, Unicode characters may occur directly within the literal strings in UTF-8 encoding, or UTF-16. (The former requires a BOM or "use utf8", the latter requires a BOM.)
Unicode characters can also be added to a string by using the "\x{...}" notation. The Unicode code for the desired character, in hexadecimal, should be placed in the braces. For instance, a smiley face is "\x{263A}". This encoding scheme works for all characters, but for characters under 0x100, note that Perl may use an 8 bit encoding internally, for optimization and/or backward compatibility.
Additionally, if you
use charnames ':full';
you can use the "\N{...}" notation and put the official Unicode character name within the braces, such as "\N{WHITE SMILING FACE}".
- *
- If an appropriate encoding is specified, identifiers within the Perl script may contain Unicode alphanumeric characters, including ideographs. Perl does not currently attempt to canonicalize variable names.
- *
- Regular expressions match characters instead of bytes. ``.'' matches a character instead of a byte.
- *
- Character classes in regular expressions match characters instead of bytes and match against the character properties specified in the Unicode properties database. "\w" can be used to match a Japanese ideograph, for instance.
- *
-
Named Unicode properties, scripts, and block ranges may be used like
character classes via the "\p{}" ``matches property'' construct and
the "\P{}" negation, ``doesn't match property''.
See ``Unicode Character Properties'' for more details.
You can define your own character properties and use them in the regular expression with the "\p{}" or "\P{}" construct.
See ``User-Defined Character Properties'' for more details.
- *
- The special pattern "\X" matches any extended Unicode sequence--``a combining character sequence'' in Standardese---where the first character is a base character and subsequent characters are mark characters that apply to the base character. "\X" is equivalent to "(?>\PM\pM*)".
- *
- The "tr///" operator translates characters instead of bytes. Note that the "tr///CU" functionality has been removed. For similar functionality see pack('U0', ...) and pack('C0', ...).
- *
- Case translation operators use the Unicode case translation tables when character input is provided. Note that "uc()", or "\U" in interpolated strings, translates to uppercase, while "ucfirst", or "\u" in interpolated strings, translates to titlecase in languages that make the distinction.
- *
- Most operators that deal with positions or lengths in a string will automatically switch to using character positions, including "chop()", "chomp()", "substr()", "pos()", "index()", "rindex()", "sprintf()", "write()", and "length()". An operator that specifically does not switch is "vec()". Operators that really don't care include operators that treat strings as a bucket of bits such as "sort()", and operators dealing with filenames.
- *
-
The "pack()"/"unpack()" letter "C" does not change, since it is often
used for byte-oriented formats. Again, think "char" in the C language.
There is a new "U" specifier that converts between Unicode characters and code points. There is also a "W" specifier that is the equivalent of "chr"/"ord" and properly handles character values even if they are above 255.
- *
- The "chr()" and "ord()" functions work on characters, similar to "pack("W")" and "unpack("W")", not "pack("C")" and "unpack("C")". "pack("C")" and "unpack("C")" are methods for emulating byte-oriented "chr()" and "ord()" on Unicode strings. While these methods reveal the internal encoding of Unicode strings, that is not something one normally needs to care about at all.
- *
- The bit string operators, "& | ^ ~", can operate on character data. However, for backward compatibility, such as when using bit string operations when characters are all less than 256 in ordinal value, one should not use "~" (the bit complement) with characters of both values less than 256 and values greater than 256. Most importantly, DeMorgan's laws ("~($x|$y) eq ~$x&~$y" and "~($x&$y) eq ~$x|~$y") will not hold. The reason for this mathematical faux pas is that the complement cannot return both the 8-bit (byte-wide) bit complement and the full character-wide bit complement.
- *
-
lc(), uc(), lcfirst(), and ucfirst() work for the following cases:
-
- *
- the case mapping is from a single Unicode character to another single Unicode character, or
- *
- the case mapping is from a single Unicode character to more than one Unicode character.
-
Things to do with locales (Lithuanian, Turkish, Azeri) do not work since Perl does not understand the concept of Unicode locales.
See the Unicode Technical Report #21, Case Mappings, for more details.
But you can also define your own mappings to be used in the lc(), lcfirst(), uc(), and ucfirst() (or their string-inlined versions).
See ``User-Defined Case Mappings'' for more details.
-
- *
- And finally, "scalar reverse()" reverses by character rather than by byte.
Unicode Character Properties
Named Unicode properties, scripts, and block ranges may be used like character classes via the "\p{}" ``matches property'' construct and the "\P{}" negation, ``doesn't match property''.For instance, "\p{Lu}" matches any character with the Unicode ``Lu'' (Letter, uppercase) property, while "\p{M}" matches any character with an ``M'' (mark---accents and such) property. Brackets are not required for single letter properties, so "\p{M}" is equivalent to "\pM". Many predefined properties are available, such as "\p{Mirrored}" and "\p{Tibetan}".
The official Unicode script and block names have spaces and dashes as separators, but for convenience you can use dashes, spaces, or underbars, and case is unimportant. It is recommended, however, that for consistency you use the following naming: the official Unicode script, property, or block name (see below for the additional rules that apply to block names) with whitespace and dashes removed, and the words ``uppercase-first-lowercase-rest''. "Latin-1 Supplement" thus becomes "Latin1Supplement".
You can also use negation in both "\p{}" and "\P{}" by introducing a caret (^) between the first brace and the property name: "\p{^Tamil}" is equal to "\P{Tamil}".
NOTE: the properties, scripts, and blocks listed here are as of Unicode 5.0.0 in July 2006.
- General Category
-
Here are the basic Unicode General Category properties, followed by their
long form. You can use either; "\p{Lu}" and "\p{UppercaseLetter}",
for instance, are identical.
Short Long L Letter LC CasedLetter Lu UppercaseLetter Ll LowercaseLetter Lt TitlecaseLetter Lm ModifierLetter Lo OtherLetter M Mark Mn NonspacingMark Mc SpacingMark Me EnclosingMark N Number Nd DecimalNumber Nl LetterNumber No OtherNumber P Punctuation Pc ConnectorPunctuation Pd DashPunctuation Ps OpenPunctuation Pe ClosePunctuation Pi InitialPunctuation (may behave like Ps or Pe depending on usage) Pf FinalPunctuation (may behave like Ps or Pe depending on usage) Po OtherPunctuation S Symbol Sm MathSymbol Sc CurrencySymbol Sk ModifierSymbol So OtherSymbol Z Separator Zs SpaceSeparator Zl LineSeparator Zp ParagraphSeparator C Other Cc Control Cf Format Cs Surrogate (not usable) Co PrivateUse Cn Unassigned
Single-letter properties match all characters in any of the two-letter sub-properties starting with the same letter. "LC" and "L&" are special cases, which are aliases for the set of "Ll", "Lu", and "Lt".
Because Perl hides the need for the user to understand the internal representation of Unicode characters, there is no need to implement the somewhat messy concept of surrogates. "Cs" is therefore not supported.
- Bidirectional Character Types
-
Because scripts differ in their directionality---Hebrew is
written right to left, for example---Unicode supplies these properties in
the BidiClass class:
Property Meaning L Left-to-Right LRE Left-to-Right Embedding LRO Left-to-Right Override R Right-to-Left AL Right-to-Left Arabic RLE Right-to-Left Embedding RLO Right-to-Left Override PDF Pop Directional Format EN European Number ES European Number Separator ET European Number Terminator AN Arabic Number CS Common Number Separator NSM Non-Spacing Mark BN Boundary Neutral B Paragraph Separator S Segment Separator WS Whitespace ON Other Neutrals
For example, "\p{BidiClass:R}" matches characters that are normally written right to left.
- Scripts
-
The script names which can be used by "\p{...}" and "\P{...}",
such as in "\p{Latin}" or "\p{Cyrillic}", are as follows:
Arabic Armenian Balinese Bengali Bopomofo Braille Buginese Buhid CanadianAboriginal Cherokee Coptic Cuneiform Cypriot Cyrillic Deseret Devanagari Ethiopic Georgian Glagolitic Gothic Greek Gujarati Gurmukhi Han Hangul Hanunoo Hebrew Hiragana Inherited Kannada Katakana Kharoshthi Khmer Lao Latin Limbu LinearB Malayalam Mongolian Myanmar NewTaiLue Nko Ogham OldItalic OldPersian Oriya Osmanya PhagsPa Phoenician Runic Shavian Sinhala SylotiNagri Syriac Tagalog Tagbanwa TaiLe Tamil Telugu Thaana Thai Tibetan Tifinagh Ugaritic Yi
- Extended property classes
-
Extended property classes can supplement the basic
properties, defined by the PropList Unicode database:
ASCIIHexDigit BidiControl Dash Deprecated Diacritic Extender HexDigit Hyphen Ideographic IDSBinaryOperator IDSTrinaryOperator JoinControl LogicalOrderException NoncharacterCodePoint OtherAlphabetic OtherDefaultIgnorableCodePoint OtherGraphemeExtend OtherIDStart OtherIDContinue OtherLowercase OtherMath OtherUppercase PatternSyntax PatternWhiteSpace QuotationMark Radical SoftDotted STerm TerminalPunctuation UnifiedIdeograph VariationSelector WhiteSpace
and there are further derived properties:
Alphabetic = Lu + Ll + Lt + Lm + Lo + Nl + OtherAlphabetic Lowercase = Ll + OtherLowercase Uppercase = Lu + OtherUppercase Math = Sm + OtherMath IDStart = Lu + Ll + Lt + Lm + Lo + Nl + OtherIDStart IDContinue = IDStart + Mn + Mc + Nd + Pc + OtherIDContinue DefaultIgnorableCodePoint = OtherDefaultIgnorableCodePoint + Cf + Cc + Cs + Noncharacters + VariationSelector - WhiteSpace - FFF9..FFFB (Annotation Characters) Any = Any code points (i.e. U+0000 to U+10FFFF) Assigned = Any non-Cn code points (i.e. synonym for \P{Cn}) Unassigned = Synonym for \p{Cn} ASCII = ASCII (i.e. U+0000 to U+007F) Common = Any character (or unassigned code point) not explicitly assigned to a script
- Use of Is Prefix
- For backward compatibility (with Perl 5.6), all properties mentioned so far may have "Is" prepended to their name, so "\P{IsLu}", for example, is equal to "\P{Lu}".
- Blocks
-
In addition to scripts, Unicode also defines blocks of
characters. The difference between scripts and blocks is that the
concept of scripts is closer to natural languages, while the concept
of blocks is more of an artificial grouping based on groups of 256
Unicode characters. For example, the "Latin" script contains letters
from many blocks but does not contain all the characters from those
blocks. It does not, for example, contain digits, because digits are
shared across many scripts. Digits and similar groups, like
punctuation, are in a category called "Common".
For more about scripts, see the UAX#24 ``Script Names'':
http://www.unicode.org/reports/tr24/
For more about blocks, see:
http://www.unicode.org/Public/UNIDATA/Blocks.txt
Block names are given with the "In" prefix. For example, the Katakana block is referenced via "\p{InKatakana}". The "In" prefix may be omitted if there is no naming conflict with a script or any other property, but it is recommended that "In" always be used for block tests to avoid confusion.
 The subroutines can be defined in any package. The user-defined properties can be used in the regular expression "\p" and "\P" constructs; if you are using a user-defined property from a package other than the one you are in, you must specify its package in the "\p" or "\P" construct.
# assuming property IsForeign defined in Lang:: package main; # property package name required if ($txt =~ /\p{Lang::IsForeign}+/) { ... } package Lang; # property package name not required if ($txt =~ /\p{IsForeign}+/) { ... }
Note that the effect is compile-time and immutable once defined.
The subroutines must return a specially-formatted string, with one or more newline-separated lines. Each line must be one of the following:
- *
- A single hexadecimal number denoting a Unicode code point to include.
- *
- Two hexadecimal numbers separated by horizontal whitespace (space or tabular characters) denoting a range of Unicode code points to include.
- *
- Something to include, prefixed by ``+'': a built-in character property (prefixed by ``utf8::'') or a user-defined character property, to represent all the characters in that property; two hexadecimal code points for a range; or a single hexadecimal code point.
- *
- Something to exclude, prefixed by ``-'': an existing character property (prefixed by ``utf8::'') or a user-defined character property, to represent all the characters in that property; two hexadecimal code points for a range; or a single hexadecimal code point.
- *
- Something to negate, prefixed ``!'': an existing character property (prefixed by ``utf8::'') or a user-defined character property, to represent all the characters in that property; two hexadecimal code points for a range; or a single hexadecimal code point.
- *
- Something to intersect with, prefixed by ``&'': an existing character property (prefixed by ``utf8::'') or a user-defined character property, for all the characters except the characters in the property; two hexadecimal code points for a range; or a single hexadecimal code point.
For example, to define a property that covers both the Japanese syllabaries (hiragana and katakana), you can define
sub InKana { return <<END; 3040\t309F 30A0\t30FF END }
Imagine that the here-doc end marker is at the beginning of the line. Now you can use "\p{InKana}" and "\P{InKana}".
You could also have used the existing block property names:
sub InKana { return <<'END'; +utf8::InHiragana +utf8::InKatakana END }
Suppose you wanted to match only the allocated characters, not the raw block ranges: in other words, you want to remove the non-characters:
sub InKana { return <<'END'; +utf8::InHiragana +utf8::InKatakana -utf8::IsCn END }
The negation is useful for defining (surprise!) negated classes.
sub InNotKana { return <<'END'; !utf8::InHiragana -utf8::InKatakana +utf8::IsCn END }
Intersection is useful for getting the common characters matched by two (or more) classes.
sub InFooAndBar { return <<'END'; +main::Foo &main::Bar END }
It's important to remember not to use ``&'' for the first set --- that would be intersecting with nothing (resulting in an empty set).
User-Defined Case Mappings
You can also define your own mappings to be used in the lc(), lcfirst(), uc(), and ucfirst() (or their string-inlined versions). The principle is similar to that of user-defined character properties: to define subroutines in the "main" package with names like "ToLower" (for lc() and lcfirst()), "ToTitle" (for the first character in ucfirst()), and "ToUpper" (for uc(), and the rest of the characters in ucfirst()).The string returned by the subroutines needs now to be three hexadecimal numbers separated by tabulators: start of the source range, end of the source range, and start of the destination range. For example:
sub ToUpper { return <<END; 0061\t0063\t0041 END }
defines an uc() mapping that causes only the characters ``a'', ``b'', and ``c'' to be mapped to ``A'', ``B'', ``C'', all other characters will remain unchanged.
If there is no source range to speak of, that is, the mapping is from a single character to another single character, leave the end of the source range empty, but the two tabulator characters are still needed. For example:
sub ToLower { return <<END; 0041\t\t0061 END }
defines a lc() mapping that causes only ``A'' to be mapped to ``a'', all other characters will remain unchanged.
(For serious hackers only) If you want to introspect the default mappings, you can find the data in the directory $Config{privlib}/unicore/To/. The mapping data is returned as the here-document, and the "utf8::ToSpecFoo" are special exception mappings derived from <$Config{privlib}>/unicore/SpecialCasing.txt. The "Digit" and "Fold" mappings that one can see in the directory are not directly user-accessible, one can use either the "Unicode::UCD" module, or just match case-insensitively (that's when the "Fold" mapping is used).
A final note on the user-defined case mappings: they will be used only if the scalar has been marked as having Unicode characters. Old byte-style strings will not be affected.
Character Encodings for Input and Output
See Encode.Unicode Regular Expression Support Level
The following list of Unicode support for regular expressions describes all the features currently supported. The references to ``Level N'' and the section numbers refer to the Unicode Technical Standard #18, ``Unicode Regular Expressions'', version 11, in May 2005.- *
-
Level 1 - Basic Unicode Support
RL1.1 Hex Notation - done [1] RL1.2 Properties - done [2][3] RL1.2a Compatibility Properties - done [4] RL1.3 Subtraction and Intersection - MISSING [5] RL1.4 Simple Word Boundaries - done [6] RL1.5 Simple Loose Matches - done [7] RL1.6 Line Boundaries - MISSING [8] RL1.7 Supplementary Code Points - done [9] [1] \x{...} [2] \p{...} \P{...} [3] supports not only minimal list (general category, scripts, Alphabetic, Lowercase, Uppercase, WhiteSpace, NoncharacterCodePoint, DefaultIgnorableCodePoint, Any, ASCII, Assigned), but also bidirectional types, blocks, etc. (see "Unicode Character Properties") [4] \d \D \s \S \w \W \X [:prop:] [:^prop:] [5] can use regular expression look-ahead [a] or user-defined character properties [b] to emulate set operations [6] \b \B [7] note that Perl does Full case-folding in matching, not Simple: for example U+1F88 is equivalent to U+1F00 U+03B9, not with 1F80. This difference matters mainly for certain Greek capital letters with certain modifiers: the Full case-folding decomposes the letter, while the Simple case-folding would map it to a single character. [8] should do ^ and $ also on U+000B (\v in C), FF (\f), CR (\r), CRLF (\r\n), NEL (U+0085), LS (U+2028), and PS (U+2029); should also affect <>, $., and script line numbers; should not split lines within CRLF [c] (i.e. there is no empty line between \r and \n) [9] UTF-8/UTF-EBDDIC used in perl allows not only U+10000 to U+10FFFF but also beyond U+10FFFF [d]
[a] You can mimic class subtraction using lookahead. For example, what UTS#18 might write as
[{Greek}-[{UNASSIGNED}]]
in Perl can be written as:
(?!\p{Unassigned})\p{InGreekAndCoptic} (?=\p{Assigned})\p{InGreekAndCoptic}
But in this particular example, you probably really want
\p{GreekAndCoptic}
which will match assigned characters known to be part of the Greek script.
Also see the Unicode::Regex::Set module, it does implement the full UTS#18 grouping, intersection, union, and removal (subtraction) syntax.
[b] '+' for union, '-' for removal (set-difference), '&' for intersection (see ``User-Defined Character Properties'')
[c] Try the ":crlf" layer (see PerlIO).
[d] Avoid "use warning 'utf8';" (or say "no warning 'utf8';") to allow U+FFFF ("\x{FFFF}").
- *
-
Level 2 - Extended Unicode Support
RL2.1 Canonical Equivalents - MISSING [10][11] RL2.2 Default Grapheme Clusters - MISSING [12][13] RL2.3 Default Word Boundaries - MISSING [14] RL2.4 Default Loose Matches - MISSING [15] RL2.5 Name Properties - MISSING [16] RL2.6 Wildcard Properties - MISSING [10] see UAX#15 "Unicode Normalization Forms" [11] have Unicode::Normalize but not integrated to regexes [12] have \X but at this level . should equal that [13] UAX#29 "Text Boundaries" considers CRLF and Hangul syllable clusters as a single grapheme cluster. [14] see UAX#29, Word Boundaries [15] see UAX#21 "Case Mappings" [16] have \N{...} but neither compute names of CJK Ideographs and Hangul Syllables nor use a loose match [e]
[e] "\N{...}" allows namespaces (see charnames).
- *
-
Level 3 - Tailored Support
RL3.1 Tailored Punctuation - MISSING RL3.2 Tailored Grapheme Clusters - MISSING [17][18] RL3.3 Tailored Word Boundaries - MISSING RL3.4 Tailored Loose Matches - MISSING RL3.5 Tailored Ranges - MISSING RL3.6 Context Matching - MISSING [19] RL3.7 Incremental Matches - MISSING ( RL3.8 Unicode Set Sharing ) RL3.9 Possible Match Sets - MISSING RL3.10 Folded Matching - MISSING [20] RL3.11 Submatchers - MISSING [17] see UAX#10 "Unicode Collation Algorithms" [18] have Unicode::Collate but not integrated to regexes [19] have (?<=x) and (?=x), but look-aheads or look-behinds should see outside of the target substring [20] need insensitive matching for linguistic features other than case; for example, hiragana to katakana, wide and narrow, simplified Han to traditional Han (see UTR#30 "Character Foldings")
Unicode Encodings
Unicode characters are assigned to code points, which are abstract numbers. To use these numbers, various encodings are needed.- *
-
UTF-8
UTF-8 is a variable-length (1 to 6 bytes, current character allocations require 4 bytes), byte-order independent encoding. For ASCII (and we really do mean 7-bit ASCII, not another 8-bit encoding), UTF-8 is transparent.
The following table is from Unicode 3.2.
Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte U+0000..U+007F 00..7F U+0080..U+07FF C2..DF 80..BF U+0800..U+0FFF E0 A0..BF 80..BF U+1000..U+CFFF E1..EC 80..BF 80..BF U+D000..U+D7FF ED 80..9F 80..BF U+D800..U+DFFF ******* ill-formed ******* U+E000..U+FFFF EE..EF 80..BF 80..BF U+10000..U+3FFFF F0 90..BF 80..BF 80..BF U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF U+100000..U+10FFFF F4 80..8F 80..BF 80..BF
Note the "A0..BF" in "U+0800..U+0FFF", the "80..9F" in "U+D000...U+D7FF", the "90..B"F in "U+10000..U+3FFFF", and the "80...8F" in "U+100000..U+10FFFF". The ``gaps'' are caused by legal UTF-8 avoiding non-shortest encodings: it is technically possible to UTF-8-encode a single code point in different ways, but that is explicitly forbidden, and the shortest possible encoding should always be used. So that's what Perl does.
Another way to look at it is via bits:
Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte 0aaaaaaa 0aaaaaaa 00000bbbbbaaaaaa 110bbbbb 10aaaaaa ccccbbbbbbaaaaaa 1110cccc 10bbbbbb 10aaaaaa 00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa
As you can see, the continuation bytes all begin with 10, and the leading bits of the start byte tell how many bytes the are in the encoded character.
- *
-
UTF-EBCDIC
Like UTF-8 but EBCDIC-safe, in the way that UTF-8 is ASCII-safe.
- *
-
UTF-16, UTF-16BE, UTF-16LE, Surrogates, and BOMs (Byte Order Marks)
The followings items are mostly for reference and general Unicode knowledge, Perl doesn't use these constructs internally.
UTF-16 is a 2 or 4 byte encoding. The Unicode code points "U+0000..U+FFFF" are stored in a single 16-bit unit, and the code points "U+10000..U+10FFFF" in two 16-bit units. The latter case is using surrogates, the first 16-bit unit being the high surrogate, and the second being the low surrogate.
Surrogates are code points set aside to encode the "U+10000..U+10FFFF" range of Unicode code points in pairs of 16-bit units. The high surrogates are the range "U+D800..U+DBFF", and the low surrogates are the range "U+DC00..U+DFFF". The surrogate encoding is
$hi = ($uni - 0x10000) / 0x400 + 0xD800; $lo = ($uni - 0x10000) % 0x400 + 0xDC00;
and the decoding is
$uni = 0x10000 + ($hi - 0xD800) * 0x400 + ($lo - 0xDC00);
If you try to generate surrogates (for example by using chr()), you will get a warning if warnings are turned on, because those code points are not valid for a Unicode character.
Because of the 16-bitness, UTF-16 is byte-order dependent. UTF-16 itself can be used for in-memory computations, but if storage or transfer is required either UTF-16BE (big-endian) or UTF-16LE (little-endian) encodings must be chosen.
This introduces another problem: what if you just know that your data is UTF-16, but you don't know which endianness? Byte Order Marks, or BOMs, are a solution to this. A special character has been reserved in Unicode to function as a byte order marker: the character with the code point "U+FEFF" is the BOM.
The trick is that if you read a BOM, you will know the byte order, since if it was written on a big-endian platform, you will read the bytes "0xFE 0xFF", but if it was written on a little-endian platform, you will read the bytes "0xFF 0xFE". (And if the originating platform was writing in UTF-8, you will read the bytes "0xEF 0xBB 0xBF".)
The way this trick works is that the character with the code point "U+FFFE" is guaranteed not to be a valid Unicode character, so the sequence of bytes "0xFF 0xFE" is unambiguously ``BOM, represented in little-endian format'' and cannot be "U+FFFE", represented in big-endian format".
- *
-
UTF-32, UTF-32BE, UTF-32LE
The UTF-32 family is pretty much like the UTF-16 family, expect that the units are 32-bit, and therefore the surrogate scheme is not needed. The BOM signatures will be "0x00 0x00 0xFE 0xFF" for BE and "0xFF 0xFE 0x00 0x00" for LE.
- *
-
UCS-2, UCS-4
Encodings defined by the ISO 10646 standard. UCS-2 is a 16-bit encoding. Unlike UTF-16, UCS-2 is not extensible beyond "U+FFFF", because it does not use surrogates. UCS-4 is a 32-bit encoding, functionally identical to UTF-32.
- *
-
UTF-7
A seven-bit safe (non-eight-bit) encoding, which is useful if the transport or storage is not eight-bit safe. Defined by RFC 2152.
Security Implications of Unicode
- *
-
Malformed UTF-8
Unfortunately, the specification of UTF-8 leaves some room for interpretation of how many bytes of encoded output one should generate from one input Unicode character. Strictly speaking, the shortest possible sequence of UTF-8 bytes should be generated, because otherwise there is potential for an input buffer overflow at the receiving end of a UTF-8 connection. Perl always generates the shortest length UTF-8, and with warnings on Perl will warn about non-shortest length UTF-8 along with other malformations, such as the surrogates, which are not real Unicode code points.
- *
-
Regular expressions behave slightly differently between byte data and
character (Unicode) data. For example, the ``word character'' character
class "\w" will work differently depending on if data is eight-bit bytes
or Unicode.
In the first case, the set of "\w" characters is either small---the default set of alphabetic characters, digits, and the ``_''--or, if you are using a locale (see perllocale), the "\w" might contain a few more letters according to your language and country.
In the second case, the "\w" set of characters is much, much larger. Most importantly, even in the set of the first 256 characters, it will probably match different characters: unlike most locales, which are specific to a language and country pair, Unicode classifies all the characters that are letters somewhere as "\w". For example, your locale might not think that LATIN SMALL LETTER ETH is a letter (unless you happen to speak Icelandic), but Unicode does.
As discussed elsewhere, Perl has one foot (two hooves?) planted in each of two worlds: the old world of bytes and the new world of characters, upgrading from bytes to characters when necessary. If your legacy code does not explicitly use Unicode, no automatic switch-over to characters should happen. Characters shouldn't get downgraded to bytes, either. It is possible to accidentally mix bytes and characters, however (see perluniintro), in which case "\w" in regular expressions might start behaving differently. Review your code. Use warnings and the "strict" pragma.
Unicode in Perl on EBCDIC
The way Unicode is handled on EBCDIC platforms is still experimental. On such platforms, references to UTF-8 encoding in this document and elsewhere should be read as meaning the UTF-EBCDIC specified in Unicode Technical Report 16, unless ASCII vs. EBCDIC issues are specifically discussed. There is no "utfebcdic" pragma or ``:utfebcdic'' layer; rather, ``utf8'' and ``:utf8'' are reused to mean the platform's ``natural'' 8-bit encoding of Unicode. See perlebcdic for more discussion of the issues.Locales
Usually locale settings and Unicode do not affect each other, but there are a couple of exceptions:- *
- You can enable automatic UTF-8-ification of your standard file handles, default "open()" layer, and @ARGV by using either the "-C" command line switch or the "PERL_UNICODE" environment variable, see perlrun for the documentation of the "-C" switch.
- *
- Perl tries really hard to work both with Unicode and the old byte-oriented world. Most often this is nice, but sometimes Perl's straddling of the proverbial fence causes problems.
When Unicode Does Not Happen
While Perl does have extensive ways to input and output in Unicode, and few other 'entry points' like the @ARGV which can be interpreted as Unicode (UTF-8), there still are many places where Unicode (in some encoding or another) could be given as arguments or received as results, or both, but it is not.The following are such interfaces. For all of these interfaces Perl currently (as of 5.8.3) simply assumes byte strings both as arguments and results, or UTF-8 strings if the "encoding" pragma has been used.
One reason why Perl does not attempt to resolve the role of Unicode in this cases is that the answers are highly dependent on the operating system and the file system(s). For example, whether filenames can be in Unicode, and in exactly what kind of encoding, is not exactly a portable concept. Similarly for the qx and system: how well will the 'command line interface' (and which of them?) handle Unicode?
- *
- chdir, chmod, chown, chroot, exec, link, lstat, mkdir, rename, rmdir, stat, symlink, truncate, unlink, utime, -X
- *
- %ENV
- *
- glob (aka the <*>)
- *
- open, opendir, sysopen
- *
- qx (aka the backtick operator), system
- *
- readdir, readlink
Forcing Unicode in Perl (Or Unforcing Unicode in Perl)
Sometimes (see ``When Unicode Does Not Happen'') there are situations where you simply need to force a byte string into UTF-8, or vice versa. The low-level calls utf8::upgrade($bytestring) and utf8::downgrade($utf8string[, FAIL_OK]) are the answers.Note that utf8::downgrade() can fail if the string contains characters that don't fit into a byte.
Using Unicode in XS
If you want to handle Perl Unicode in XS extensions, you may find the following C APIs useful. See also ``Unicode Support'' in perlguts for an explanation about Unicode at the XS level, and perlapi for the API details.- *
- "DO_UTF8(sv)" returns true if the "UTF8" flag is on and the bytes pragma is not in effect. "SvUTF8(sv)" returns true if the "UTF8" flag is on; the bytes pragma is ignored. The "UTF8" flag being on does not mean that there are any characters of code points greater than 255 (or 127) in the scalar or that there are even any characters in the scalar. What the "UTF8" flag means is that the sequence of octets in the representation of the scalar is the sequence of UTF-8 encoded code points of the characters of a string. The "UTF8" flag being off means that each octet in this representation encodes a single character with code point 0..255 within the string. Perl's Unicode model is not to use UTF-8 until it is absolutely necessary.
- *
- "uvchr_to_utf8(buf, chr)" writes a Unicode character code point into a buffer encoding the code point as UTF-8, and returns a pointer pointing after the UTF-8 bytes. It works appropriately on EBCDIC machines.
- *
- "utf8_to_uvchr(buf, lenp)" reads UTF-8 encoded bytes from a buffer and returns the Unicode character code point and, optionally, the length of the UTF-8 byte sequence. It works appropriately on EBCDIC machines.
- *
- "utf8_length(start, end)" returns the length of the UTF-8 encoded buffer in characters. "sv_len_utf8(sv)" returns the length of the UTF-8 encoded scalar.
- *
- "sv_utf8_upgrade(sv)" converts the string of the scalar to its UTF-8 encoded form. "sv_utf8_downgrade(sv)" does the opposite, if possible. "sv_utf8_encode(sv)" is like sv_utf8_upgrade except that it does not set the "UTF8" flag. "sv_utf8_decode()" does the opposite of "sv_utf8_encode()". Note that none of these are to be used as general-purpose encoding or decoding interfaces: "use Encode" for that. "sv_utf8_upgrade()" is affected by the encoding pragma but "sv_utf8_downgrade()" is not (since the encoding pragma is designed to be a one-way street).
- *
- is_utf8_char(s) returns true if the pointer points to a valid UTF-8 character.
- *
- "is_utf8_string(buf, len)" returns true if "len" bytes of the buffer are valid UTF-8.
- *
- "UTF8SKIP(buf)" will return the number of bytes in the UTF-8 encoded character in the buffer. "UNISKIP(chr)" will return the number of bytes required to UTF-8-encode the Unicode character code point. "UTF8SKIP()" is useful for example for iterating over the characters of a UTF-8 encoded buffer; "UNISKIP()" is useful, for example, in computing the size required for a UTF-8 encoded buffer.
- *
- "utf8_distance(a, b)" will tell the distance in characters between the two pointers pointing to the same UTF-8 encoded buffer.
- *
- "utf8_hop(s, off)" will return a pointer to a UTF-8 encoded buffer that is "off" (positive or negative) Unicode characters displaced from the UTF-8 buffer "s". Be careful not to overstep the buffer: "utf8_hop()" will merrily run off the end or the beginning of the buffer if told to do so.
- *
- "pv_uni_display(dsv, spv, len, pvlim, flags)" and "sv_uni_display(dsv, ssv, pvlim, flags)" are useful for debugging the output of Unicode strings and scalars. By default they are useful only for debugging---they display all characters as hexadecimal code points---but with the flags "UNI_DISPLAY_ISPRINT", "UNI_DISPLAY_BACKSLASH", and "UNI_DISPLAY_QQ" you can make the output more readable.
- *
- "ibcmp_utf8(s1, pe1, l1, u1, s2, pe2, l2, u2)" can be used to compare two strings case-insensitively in Unicode. For case-sensitive comparisons you can just use "memEQ()" and "memNE()" as usual.
For more information, see perlapi, and utf8.c and utf8.h in the Perl source code distribution.
BUGS
Interaction with Locales
Use of locales with Unicode data may lead to odd results. Currently, Perl attempts to attach 8-bit locale info to characters in the range 0..255, but this technique is demonstrably incorrect for locales that use characters above that range when mapped into Unicode. Perl's Unicode support will also tend to run slower. Use of locales with Unicode is discouraged.Problems with characters whose ordinal numbers are in the range 128 - 255 with no Locale specified
Without a locale specified, unlike all other characters or code points, these characters have very different semantics in byte semantics versus character semantics. In character semantics they are interpreted as Unicode code points, which means they are viewed as Latin-1 (ISO-8859-1). In byte semantics, they are considered to be unassigned characters, meaning that the only semantics they have is their ordinal numbers, and that they are not members of various character classes. None are considered to match "\w" for example, but all match "\W". Besides these class matches, the known operations that this affects are those that change the case, regular expression matching while ignoring case, and quotemeta(). This can lead to unexpected results in which a string's semantics suddenly change if a code point above 255 is appended to or removed from it, which changes the string's semantics from byte to character or vice versa. This behavior is scheduled to change in version 5.12, but in the meantime, a workaround is to always call utf8::upgrade($string), or to use the standard modules Encode or charnames.Interaction with Extensions
When Perl exchanges data with an extension, the extension should be able to understand the UTF8 flag and act accordingly. If the extension doesn't know about the flag, it's likely that the extension will return incorrectly-flagged data.So if you're working with Unicode data, consult the documentation of every module you're using if there are any issues with Unicode data exchange. If the documentation does not talk about Unicode at all, suspect the worst and probably look at the source to learn how the module is implemented. Modules written completely in Perl shouldn't cause problems. Modules that directly or indirectly access code written in other programming languages are at risk.
For affected functions, the simple strategy to avoid data corruption is to always make the encoding of the exchanged data explicit. Choose an encoding that you know the extension can handle. Convert arguments passed to the extensions to that encoding and convert results back from that encoding. Write wrapper functions that do the conversions for you, so you can later change the functions when the extension catches up.
To provide an example, let's say the popular Foo::Bar::escape_html function doesn't deal with Unicode data yet. The wrapper function would convert the argument to raw UTF-8 and convert the result back to Perl's internal representation like so:
sub my_escape_html ($) { my($what) = shift; return unless defined $what; Encode::decode_utf8(Foo::Bar::escape_html(Encode::encode_utf8($what))); }
Sometimes, when the extension does not convert data but just stores and retrieves them, you will be in a position to use the otherwise dangerous Encode::_utf8_on() function. Let's say the popular "Foo::Bar" extension, written in C, provides a "param" method that lets you store and retrieve data according to these prototypes:
$self->param($name, $value); # set a scalar $value = $self->param($name); # retrieve a scalar
If it does not yet provide support for any encoding, one could write a derived class with such a "param" method:
sub param { my($self,$name,$value) = @_; utf8::upgrade($name); # make sure it is UTF-8 encoded if (defined $value) { utf8::upgrade($value); # make sure it is UTF-8 encoded return $self->SUPER::param($name,$value); } else { my $ret = $self->SUPER::param($name); Encode::_utf8_on($ret); # we know, it is UTF-8 encoded return $ret; } }
Some extensions provide filters on data entry/exit points, such as DB_File::filter_store_key and family. Look out for such filters in the documentation of your extensions, they can make the transition to Unicode data much easier.
Speed
Some functions are slower when working on UTF-8 encoded strings than on byte encoded strings. All functions that need to hop over characters such as length(), substr() or index(), or matching regular expressions can work much faster when the underlying data are byte-encoded.In Perl 5.8.0 the slowness was often quite spectacular; in Perl 5.8.1 a caching scheme was introduced which will hopefully make the slowness somewhat less spectacular, at least for some operations. In general, operations with UTF-8 encoded strings are still slower. As an example, the Unicode properties (character classes) like "\p{Nd}" are known to be quite a bit slower (5-20 times) than their simpler counterparts like "\d" (then again, there 268 Unicode characters matching "Nd" compared with the 10 ASCII characters matching "d").
Possible problems on EBCDIC platforms
In earlier versions, when byte and character data were concatenated, the new string was sometimes created by decoding the byte strings as ISO 8859-1 (Latin-1), even if the old Unicode string used EBCDIC.If you find any of these, please report them as bugs.
Porting code from perl-5.6.X
Perl 5.8 has a different Unicode model from 5.6. In 5.6 the programmer was required to use the "utf8" pragma to declare that a given scope expected to deal with Unicode data and had to make sure that only Unicode data were reaching that scope. If you have code that is working with 5.6, you will need some of the following adjustments to your code. The examples are written such that the code will continue to work under 5.6, so you should be safe to try them out.- *
-
A filehandle that should read or write UTF-8
if ($] > 5.007) { binmode $fh, ":encoding(utf8)"; }
- *
-
A scalar that is going to be passed to some extension
Be it Compress::Zlib, Apache::Request or any extension that has no mention of Unicode in the manpage, you need to make sure that the UTF8 flag is stripped off. Note that at the time of this writing (October 2002) the mentioned modules are not UTF-8-aware. Please check the documentation to verify if this is still true.
if ($] > 5.007) { require Encode; $val = Encode::encode_utf8($val); # make octets }
- *
-
A scalar we got back from an extension
If you believe the scalar comes back as UTF-8, you will most likely want the UTF8 flag restored:
if ($] > 5.007) { require Encode; $val = Encode::decode_utf8($val); }
- *
-
Same thing, if you are really sure it is UTF-8
if ($] > 5.007) { require Encode; Encode::_utf8_on($val); }
- *
-
A wrapper for fetchrow_array and fetchrow_hashref
When the database contains only UTF-8, a wrapper function or method is a convenient way to replace all your fetchrow_array and fetchrow_hashref calls. A wrapper function will also make it easier to adapt to future enhancements in your database driver. Note that at the time of this writing (October 2002), the DBI has no standardized way to deal with UTF-8 data. Please check the documentation to verify if that is still true.
sub fetchrow { my($self, $sth, $what) = @_; # $what is one of fetchrow_{array,hashref} if ($] < 5.007) { return $sth->$what; } else { require Encode; if (wantarray) { my @arr = $sth->$what; for (@arr) { defined && /[^\000-\177]/ && Encode::_utf8_on($_); } return @arr; } else { my $ret = $sth->$what; if (ref $ret) { for my $k (keys %$ret) { defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret->{$k}; } return $ret; } else { defined && /[^\000-\177]/ && Encode::_utf8_on($_) for $ret; return $ret; } } } }
- *
-
A large scalar that you know can only contain ASCII
Scalars that contain only ASCII and are marked as UTF-8 are sometimes a drag to your program. If you recognize such a situation, just remove the UTF8 flag:
utf8::downgrade($val) if $] > 5.007;
SEE ALSO
perlunitut, perluniintro, Encode, open, utf8, bytes, perlretut, ``${^UNICODE}'' in perlvar
Index
- NAME
- DESCRIPTION
-
- Important Caveats
- Byte and Character Semantics
- Effects of Character Semantics
- Unicode Character Properties
- User-Defined Character Properties
- User-Defined Case Mappings
- Character Encodings for Input and Output
- Unicode Regular Expression Support Level
- Unicode Encodings
- Security Implications of Unicode
- Unicode in Perl on EBCDIC
- Locales
- When Unicode Does Not Happen
- Forcing Unicode in Perl (Or Unforcing Unicode in Perl)
- Using Unicode in XS
- BUGS
- SEE ALSO
This document was created by man2html, using the manual pages.
Time: 05:29:09 GMT, December 24, 2015


Misc title with an inline html export
neato!
This is verse
or even a totally custom kind of block crazy ain't it?
see ./headlines.org
Note that only src/example/export block inclusion is supported for now. There's quite a lot more to include (see the org manual for include files) but I don't have a use case for this yet and stuff like namespacing footnotes of included files adds quite a bit of complexity.
for now files can be included as:
src block
#+SETUPFILE: setup_file_org
#+OPTIONS: toc:1
* Simple Headline [1/2]
- [X] checked
- [ ] unchecked
- note that statistic tokens are marked up anywhere
not just where they are actually meant to be - even here > [100%] <
(Org mode proper does the same)
* TODO [#B] Headline with todo status & priority
* DONE Headline with TODO status
:PROPERTIES:
:custom_id: this-will-be-the-id-of-the-headline
:note: property drawers are not exported as html like other drawers
:END:
we can link to headlines that define a custom_id: [[#this-will-be-the-id-of-the-headline]]
* [#A] Headline with tags & priority :foo:bar:
Still outside the drawer
:DRAWERNAME:
This is inside the drawer
:END:
Still outside the drawer
* CUSTOM headline with custom status
it's possible to use =#+SETUPFILE= - in this case the setup file contains the following
#+INCLUDE: "setup_file_org" src org
* excluded headline :custom_noexport:
this headline and it's content are not exported as it is marked with an =EXCLUDE_TAGS= tag.
By default =EXCLUDE_TAGS= is just =:noexport:=.
* malformed property drawer
:PROPERTIES:
not a property
:END:
* level limit for headlines to be included in the table of contents
The toc option allows setting a [[https://orgmode.org/manual/Export-settings.html][level limit]]. For this file we set it to 1 - which means that the following headlines
won't be included in the table of contents.
** headline 2 not in toc
*** headline 3 not in toc
** anoter headline 2 not in toc
you get the gist...
export block
Paragraphs are the default element.
Empty lines and other elements end paragraphs - but paragraphs can obviously span multiple lines.
Paragraphs can contain inline markup like emphasis strong and links example.com and stuff.
example block
language: go go: "1.x" script: - make test - make generate-gh-pages deploy: provider: pages github-token: $GITHUB_TOKEN # From travis-ci.org repository settings local-dir: gh-pages target-branch: gh-pages skip-cleanup: true verbose: true on: branch: master
| foo | foo |
| bar | bar |
ndash –
mdash —
ellipsis …
acute Á and so on
note that —— is replaced with 2 mdashes and …. becomes ellipsis+. and so on - that's how org also does it
code
wrapped text gets joined
either this
or that
foo.
either this
or that
foo.
this list item has multiple linbreaks - but it's still just one paragraph (i.e. no line breaks are rendered)
foobar
same goes for ordered lists
foo
bullet 1
sub bullet
code
— as code plus dash
italics
Text italics
just a space as title…
Foo paragraph.
Bar paragraph
just like #46
--
-> – (en dash)
---
-> — (em dash)
also, consecutive dashes inside
inline code --
---
and verbatim --
---
src/example/export blocks should not be converted!
--, ---
--, -----, ---
--, ---
footnotes can contain markup - and other elements and stuff 1 2
The behaviour of Org mode <s TAB
changed and it now inserts lowercased src blocks (go-org already handled this one)
lowercased:
uname -a
uppercased
uname -a
Hello, I'm writing hugo blogs using org-mode.
When inserting an image link like , hugo doesn't export the image.
(defun small-shell ()
(interactive)
(split-window-vertically)
(other-window 1)
(shrink-window (- (window-height) 12))
(ansi-term))
0\\


Career
Liên started her private practices in Lowell and later on in Woburn, where she treated patients with chronic pain, sports injuries, fibromyalgia, allergies, insomnia, infertility and women’s health, stress, neurological and digestive issues. In 2012 and 2013 her private practice, Sunrise Acupuncture, was voted “Greater Woburn’s Best Acupuncture Therapy.” Since 2011, she’s also been working at the Pain & Wellness Center with a team of doctors, nurse practitioners, and physical and massage therapists, to treat chronic and severe pain cases. Liên closed her private practice in 2014 to work at Massachusetts General Hospital (MGH Boston) treating patients in Oncology, at Beth Israel Deaconess Medical Center Cheng-Tsui Integrated Health Center (BIDMC Longwood and Chestnut Hill locations), as well as the Pain & Wellness Center. Liên reopens her private practice in the fall of 2018 because she enjoys giving personalized attention to her patients and treating one patient for the whole duration of the patient’s acupuncture session.
Education
Liên received a Bachelor's degree in Chemical Engineering from MIT and a Master’s degree in Acupuncture and Oriental Medicine (MAOM) in 2007 from the New England School of Acupunture. She went on to study Functional Medicine, Orthopedic Acupuncture, Dr. Tan’s Global Balance and Balancing Methods, Master Tung’s Points, Foot Reflexology, Tuina, non-insertive methods such as ShakuJu and Biomagnetic Acupoint Therapy, Cancer and Oriental Medicine, and Herbal Medicine for Women’s Health. In 2013, she spent ten days climbing the Emei Mountain in China, learning Emei Qigong and Tuina, meditating, and experiencing traditional Chinese culture.
For her own well-being, Liên implements natural healing through foods and natural supplements, meditation, yoga, acupuncture, massage therapy,
chiropractic care, and physical therapy.


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--- layout: archive title: Zulip Chat Archive permalink: /stream/113489-new-members/topic/refl.20for.20a.20.3D.20b.20-.3E.20a.20.3D.20b.3F.html ---
hello, how do i discharge a = b -> a = b
?
exact id
or intro H, exact H
nothing similar to refl
?
refl
says x = x
. You want x -> x
I mean, refl
should work... (if we have the right instance)
afterall ->
is a partial order
a total order if you believe in classical logic
but I don't think Mario will like the instance
i tried refl
. that didn't work. simp
worked.
@[refl] theorem testing {p : Prop} : p → p := id
invalid reflexivity rule, result type must be an operator application
so I can't tag it with refl
, but I don't understand why
maybe ->
is special
That's interesting! I was thinking along the same lines as you.
because sometimes you want extra hypotheses or something
which will be ->
But I'm still hung up in proving A x B = A x B in the other thread ;-)
so you don't want ->
to ever have other properties
I guess ->
isn't a binary relation. But it should be on Prop, right?
meta def refl' : tactic unit := `[exact id] theorem test {a b : nat} : a = b → a = b := by refl'
:P
I'm not impressed
that's not actually refl
Does library_search
find it?
Apparently not...
{% endraw %}Last updated: Apr 24 2020 at 19:02 UTC


Thailand's Coastal Water Quality
Dissolved Oxygen:
< 3 = red
3 - 7 = yellow
7 - 20 = green
Otherwise = white
Choose year:
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
play


import {NgModule} from "@angular/core";
import {CommonModule} from "@angular/common";
import {A11yModule} from "@angular/cdk/a11y";
import {IntlModule} from "@sinequa/core/intl";
// Formatting pipes
import {DatePipe} from "./pipes/date-pipe";
import {ExprPipe} from "./pipes/expr-pipe";
import {MemorySizePipe} from "./pipes/memory-size-pipe";
import {MomentPipe} from "./pipes/moment-pipe";
import {NumberPipe} from "./pipes/number-pipe";
import {RelativeTimePipe} from "./pipes/relative-time-pipe";
import {TimePipe} from "./pipes/time-pipe";
import {ValuePipe} from "./pipes/value-pipe";
// UI Directives
import {Autofocus} from "./directives/autofocus";
import {ClickOutside} from "./directives/click-outside";
import {MediaIf} from "./directives/media-if";
import {ScrollIntoView} from "./directives/scroll-into-view";
import {FocusKeyListDirective} from "./directives/focus-key-list.directive";
import {FocusKeyListItemDirective} from "./directives/focus-key-list-item.directive";
import {ResizeEventDirective} from "./directives/resize-event.directive";
import {StickyComponent} from "./directives/sticky";
import {TooltipComponent} from "./directives/tooltip/tooltip.component";
import {TooltipDirective} from "./directives/tooltip/tooltip.directive";
// UI Service
import {SCREEN_SIZE_RULES} from "./ui.service";
export const defaultScreenSizeRules = {
xxl: "(min-width: 1920px)",
xl: "(min-width: 1200px) and (max-width: 1919.98px)",
lg: "(min-width: 992px) and (max-width: 1199.98px)",
md: "(min-width: 768px) and (max-width: 991.98px)",
sm: "(min-width: 576px) and (max-width: 767.98px)",
xs: "(max-width: 575.98px)",
};
@NgModule({
imports: [
CommonModule,
A11yModule,
IntlModule
],
declarations: [
DatePipe, ExprPipe, MemorySizePipe, MomentPipe, NumberPipe, RelativeTimePipe, TimePipe, ValuePipe,
Autofocus, ClickOutside, MediaIf, ScrollIntoView, FocusKeyListDirective, FocusKeyListItemDirective,
ResizeEventDirective, StickyComponent, TooltipComponent, TooltipDirective
],
exports: [
DatePipe, ExprPipe, MemorySizePipe, MomentPipe, NumberPipe, RelativeTimePipe, TimePipe, ValuePipe,
Autofocus, ClickOutside, MediaIf, ScrollIntoView, FocusKeyListDirective, FocusKeyListItemDirective,
ResizeEventDirective, StickyComponent, TooltipComponent, TooltipDirective
],
providers: [
{
provide: SCREEN_SIZE_RULES,
useValue: defaultScreenSizeRules
}
]
})
export class UtilsModule {
}


Contributing Code
This page outlines the process for contributing code to Crosswalk. For information on obtaining the source and building Crosswalk, see Building Crosswalk.
Overview
These are the recommended steps for contributing code to Crosswalk:
- Choose or create a bug report to work on.
- Declare your "intent to implement".
- Develop your changes.
- Make sure your changes meet the code style guidelines. The check-style script may be of help.
- Run the unit tests.
- Add any new files to your working directory.
- Prepare your commit message.
- Submit your patch for review using the Github pull request system.
- Make any changes recommended by the reviewer.
- Once reviewed, the patch will be landed for you.
- Please watch for any regressions it may have caused (hopefully none)!
More detail about some of these steps is below.
Terminology
PR:
Pull request - a request (made via github) for your code to be incorporated into the main Crosswalk code base.
LGTM:
"Looks Good To Me" - an abbreviation used to confirm that a pull request, intent to implement (see below) etc. is approved by a member of the project.
Choose a bug report
The Jira issue tracker is the central point of communication for contributions to Crosswalk. Nearly every contribution corresponds to an issue there.
Choose an issue to work on, or create a new one if no suitable issue exists. To avoid duplication, be sure to search the database before creating new issues.
You should note the ID of the issue you work on, so you can include it in your "intent to implement", if you need to declare one (see below). The ID is the XWALK-N identifier at the end of the URL for the issue: for example, for https://crosswalk-project.org/jira/browse/XWALK-898, the ID is XWALK-898.
Declare your "intent to implement"
In an attempt to improve the efficiency of code reviews, we are taking a page from the Blink project and adopting the practice of "intent to implement". The idea is to let owners and other developers know what a developer (or development team) plans to implement, and when and how they intend to do it. This gives the community a chance to comment on early design choices, avoiding the cost of undoing or redoing work when an implementation is already too far ahead.
An intent to implement is required for new features, non-trivial refactoring, or for implementations which are likely to be controversial. If you're not sure whether your implementation falls into one of these categories, ask for advice about how to proceed by using the crosswalk-dev mailing list or #crosswalk IRC channel.
To declare an "intent to implement", a developer should send a mail to the crosswalk-dev mailing list following the outline below.
Subject (brief summary):
Intent to Implement <summary of intent>
Body (more detail about what is to be implemented):
Description: <what this implementation is about, what it does, why it's needed> Affected component: <affected Crosswalk component> Related feature: <Jira issue ID> Target release: <Crosswalk version number> Implementation details: <depending on the complexity, this can be a a one-liner, short discussion, or a link to a design document (e.g. Google Docs); however, we prefer that the discussion is started before extensive design is done>
The plan should be approved ("LGTM") by the relevant owner(s) before substantial work is carried out.
Develop your changes
After your "intent to implement" has been approved, you can begin working on your changes.
Make sure that any new source code you introduce contains the appropriate license text at the beginning of the file. If you are the author of a new file, the preferred license text to include can be found in the LICENSE file or any existing file.
You should also add your name to the AUTHORS file the first time you make a patch.
Code style guidelines
Patches must comply with the code style guidelines. Your patch will be automatically checked for style compliance when you upload it to the bug tracker.
See the Crosswalk coding style for details.
Commit message guidelines
Your commits and/or PRs should reference the ID of the issue you are working on. You can use issue IDs in commit messages and PRs in the following ways:
To refer to an issue from a PR, include the issue ID in the PR's description. This will result in a mention of the PR in the corresponding Crosswalk Jira issue.
For example, if you were working on issue XWALK-898, you could reference the issue in a commit message like this:
Append "-tests" to package name, as per XWALK-898.
Only opening and closing a PR (with an issue ID in the description) will result in a comment being added to Jira. Updating a PR will not update related Jira issues.
To close a related Jira issue, add a line with the format BUG=XWALK-N to a PR description (NB this is case sensitive). Doing this will resolve the corresponding issue in Jira when the PR is merged. Using the issue URL
(**BUG=https://path/to/issue/XWALK-N**)
is also acceptable.For example, if your PR closes issue XWALK-898, you could include this in the PR description:
BUG=XWALK-898
or this:
BUG=https://crosswalk-project.org/jira/browse/XWALK-898
If a PR doesn't completely fix an issue, do not use the "BUG=" prefix, but do mention the issue ID. Only use "BUG=" when the PR fixes the issue.
If a PR fixes multiple issues, reference them on separate lines of the description, starting each with "BUG=".
Note that although the prefix is "BUG=", this mechanism applies to features and tasks as well.
Regression tests
A buildbot infrastructure will be available soon. Those buildbots will run the unit tests and the browser tests.
You are responsible for keeping the tree green. If the tree is red because of your patch, it may be that your commit will be reverted if the other contributors can't reach you or can't fix the problem themselves.
Respond to reviewers
A Crosswalk reviewer must approve your patch before Crosswalk can accept it into the source control repository. A reviewer will either approve your patch by responding with "LGTM" in the pull request, or request revisions to your patch. In rare cases, a patch may be permanently rejected, meaning that the reviewer believes the feature should never be committed to the tree. The review process can consist of multiple iterations between you and the reviewer as you submit revised patches.
Obtaining commit privileges
By default, contributors do not have push rights to Crosswalk repositories. After contributing a few patches (~5-10) you may ask an OWNER to nominate you for push access. This privilege is granted with some expectation of responsibility: committers are people who care about the Crosswalk project and want to help it meet its goals. A committer is not just someone who can make changes, but someone who has demonstrated his or her ability to collaborate with the team, get the most knowledgeable people to review code, contribute high-quality code, and follow through to fix issues (in code or tests).
Obtaining review privileges
Our Reviewer policy provides details on obtaining review privileges.


%include templates/parts/head.html
%include templates/parts/navBar.htmlSome assignments offer a solution 'demo' that you can run to see the program's expected behavior. On many machines, all you have to do is download the .jar file, then double-click it to run it. But on some Macs, it won't work; your operating system will say that it doesn't know how to launch the file. If you have that issue, download the file, go to the Downloads folder in your Finder, right-click on the file, and click Open, and then press Confirm.
Some Mac users see a security error such as, "cs106b-hw1-life-demo.jar can't be opened because it is from an unidentified developer." To fix this, go to System Preferences → Security & Privacy. You will see a section about downloaded apps. You should see a prompt asking if you would like to allow access to our solution JAR. Follow the steps and then you should be able to open the demo.


Templates can have variable. To declare variable, use arrow function that doesn't return anything, and set it to this
For example:
${()=>{this.myVariable = "some_value"}}
Note that expression above allows multilne for more complex scenarios. If arrow function returns anything it will be redndered into in template. Example for multilne expression: ${ () => { this.myVariable2 = "some_value_2"; this.myVariable3 = "some_value_3"; } }
${ () => { this.myVariable2 = "some_value_2"; this.myVariable3 = "some_value_3"; } }
${()=>this.myVariable}
${(() => {this.myVariable4 = "some_value_4"})()}${(() => {this.myVariable4 = "some_value_4"})()} myVariable4 is accesible without arrow function:
${this.myVariable4}myVariable4=${this.myVariable4}


Breakdown
Reports
log
workforce
Plant
Select
AllYear
2017
2018
Select
AllLines
Line 5
Monthly
Weekly


class src.core.StrategyEvaluator(encoding='latin')[source]¶ This class implements the pipeline for various strategies. hyperparamTuning(train_data='data/dataset-string-similarity_global_1k.csv', test_data='data/dataset-string-similarity.txt')[source]¶ A complete process of distinct steps in figuring out the best ML algorithm with best hyperparameters to toponym interlinking problem. Parameters: train_data (str) – Relative path to the train dataset. test_data (str) – Relative path to the test dataset.
src.core.
StrategyEvaluator
This class implements the pipeline for various strategies.
hyperparamTuning
A complete process of distinct steps in figuring out the best ML algorithm with best hyperparameters to toponym interlinking problem.
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J-Signature Wrapper Directive.
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User Name: joni.janson
Format Name: Sample_v3, TestResultQC_v3, Batch_v3
Format Version: 3.00.29
EDD File(s):
R:\eddge\client files\NYSDEC Equis v3 RIBS\R2004683\Sample_v3.txt
R:\eddge\client files\NYSDEC Equis v3 RIBS\R2004683\TestResultQC_v3.txt
R:\eddge\client files\NYSDEC Equis v3 RIBS\R2004683\Batch_v3.txt
RefVals Set: C:\Program Files\EarthSoft\EQuIS\Formats\NYS DEC v3\NYSDEC.rvf
Run Date: 6/25/2020 7:23:54 PM
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Habibi Hookah Cafe is the perfect place for hookah smokers seeking a relaxed atmosphere during the day, and a lively atmosphere at night--complete with music, dancing, and DJs on the weekends.
We also have the best brands of tobacco, hookahs, and vapor products and supplies for sale. Current brands we serve/sell: Al Fakher, Star Buzz, Haze, Tangiers, Fumari, Social Smoke, Fantasia, and Argelini. We can also repair or customize any hookah you can bring us, we're up for the challenge!
We opened in early 2004 on South Broadway with a small staff, unsure of what the hookah business would have in store for us. Now, several years and a change in ownership later, our staff and regulars are a family, and the hookah nightlife continues to be as busy, fast-paced, and high-spirited as ever. Over the years, we've seen and done it all, in a rich cultural setting that doubles as a night club. Come see us and experience our rich history for yourselves!
2 pm
2 am


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netty in action 读书笔记
explain the transport implementations that come bundled with Netty and the use cases appropriate to each.
the superior functionality and flexibility of ByteBuf as compared to the JDK’s ByteBuffer.
a Channel has a ChannelPipeline and a ChannelConfig assigned to it. The ChannelConfig holds all of the configuration settings for the Channel and supports hot changes.
The ChannelPipeline holds all of the ChannelHandler instances that will be applied to inbound and outbound data and events.
Typical uses for ChannelHandlers include:
■ Transforming data from one format to another
■ Providing notification of exceptions
■ Providing notification of a Channel becoming active or inactive
■ Providing notification when a Channel is registered with or deregistered from an EventLoop
■ Providing notification about user-defined events
The ChannelPipeline implements a common design pattern, Intercepting Filter. UNIX pipes are another familiar example: com- mands are chained together, with the output of one command connecting to the input of the next in line.
The ChannelPipeline implements a common design pattern, Intercepting Filter. UNIX pipes are another familiar example: com- mands are chained together, with the output of one command connecting to the input of the next in line.
过滤链的设计模式，类似Unix的pipe
keep in mind that the broad range of functionality offered by Netty relies on a small number of interfaces. This means that you can make significant modifications to application logic without wholesale refactoring of your code base.
netty设计过程中注重的一个点： a small number of interfaces。
Netty’s Channel implementations are thread-safe, so you can store a reference to a Channel and use it whenever you need to write something to the remote peer, even when many threads are in use.
Channel是线程安全的。
final Channel channel = ctx.channel();
final ByteBuf buf = Unpooled.copiedBuffer("your data",
CharsetUtil.UTF_8).retain();
//新建的线程可以随便的调用
Runnable writer = new Runnable() {
@Override
public void run() {
channel.write(buf.duplicate());
}
netty支持的协议。
The basic concept behind the selector is to serve as a registry where you request to be notified when the state of a Channel changes. The possible state changes are ■ A new Channel was accepted and is ready. ■ A Channel connection was completed. ■ A Channel has data that is ready for reading. ■ A Channel is available for writing data. After the application reacts to the change of state, the selector is reset and the process repeats, running on a thread that checks for changes and responds to them accordingly.
pipeline时间的变化，底层的实现还是基于：java.nio.channels.SelectionKey.
Zero-copy
Zero-copy is a feature currently available only with NIO and Epoll transport. It allows you to quickly and efficiently move data from a file system to the network without copying from kernel space to user space, which can significantly improve perfor- mance in protocols such as FTP or HTTP. This feature is not supported by all OSes. Specifically it is not usable with file systems that implement data encryption or compression—only the raw content of a file can be transferred. Conversely, transferring files that have already been encrypted isn’t a problem.
零拷贝技术，是的netty的效率比较的高效。不支持文件系统中数据的压缩和解压缩。但是传输压缩的数据是没有问题的。
Netty’s NIO transport is based on the common abstraction for asynchronous/non-blocking networking provided by Java. Although this ensures that Netty’s non-blocking API will be usable on any platform, it also entails limitations, because the JDK has to make compromises in order to deliver the same capabilities on all systems.
netty基于JDK提动的网路通信功能，保证了平台的普适性。但是也正因为是JDK为了平台的普适性，做出了妥协。
Given this, you may wonder how Netty can support NIO with the same API used for asynchronous transports. The answer is that Netty makes use of the SO_TIMEOUT Socket flag, which specifies the maximum number of milliseconds to wait for an I/O opera- tion to complete. If the operation fails to complete within the specified interval, a SocketTimeoutException is thrown. Netty catches this exception and continues the processing loop. On the next EventLoop run, it will try again. This is the only way an asynchronous framework like Netty can support OIO
OIO和NIO实现的差别。
Netty’s API for data handling is exposed through two components—abstract class ByteBuf and interface ByteBufHolder.
These are some of the advantages of the ByteBuf API:
■ It’s extensible to userdefined buffer types.
■ Transparent zero-copy is achieved by a built-in composite buffer type.
■ Capacity is expanded on demand (as with the JDK StringBuilder).
■ Switching between reader and writer modes doesn’t require calling ByteBuffer’s flip() method.
■ Reading and writing employ distinct indices.
■ Method chaining is supported.
■ Reference counting is supported.
■ Pooling is supported.
netty中使用bytebuffer的原因：
1.易于扩展用户自定义的数据类型
2.新建类型的时候可以确定是否是Zero-Copy类型
3.自动需求自动扩展容量
4.读写之间的切换不用调用flip
5.读写标志位的分离，方法链，引用计算以及池化的支持
Because all network communications involve the movement of sequences of bytes, an efficient and easy-to-use data structure is an obvious necessity. Netty’s ByteBuf imple- mentation meets and exceeds these requirements.
netty不用JDK自带的ByteBuffer，而是自行扩展了ByteBuf的原因。
To understand the relationship between these indices, consider what would happen if you were to read bytes until the readerIndex reached the same value as the writerIndex. At that point, you would have reached the end of readable data. Attempting to read beyond that point would trigger an IndexOutOfBoundsException, just as when you attempt to access data beyond the end of an array.
ByteBuf使用了两个index，readerIndex和writerIndex，为了操作的方便。netty封装的ByteBuf的实质：an array of bytes with distinct indices to control read and write access。
另外ByteBuf提供的方法中，只有以read或者writer开头的方法名称，才会改变readindex或者writeindex的位置。
The most frequently used ByteBuf pattern stores the data in the heap space of the JVM. Referred to as a backing array, this pattern provides fast allocation and dealloca- tion in situations where pooling isn’t in use.
最常用的ByteBuf模式将数据存储在JVM的堆空间中。这一模式被称为backing array，在不使用池的情况下，该模式提供了快速分配和回收。这种分配的方式称为：heapBuffer
NOTE Attempting to access a backing array when hasArray() returns false will trigger an UnsupportedOperation- Exception. This pattern is similar to uses of the JDK’s ByteBuffer.
Direct buffer is another ByteBuf pattern. We expect that memory allocated for object creation will always come from the heap, but it doesn’t have to—the ByteBuffer class that was introduced in JDK 1.4 with NIO allows a JVM implementation to allocate memory via native calls. This aims to avoid copying the buffer’s contents to (or from) an intermediate buffer before (or after) each invocation of a native I/O operation.The Javadoc for ByteBuffer states explicitly,“The contents of direct buffers will reside outside of the normal garbage-collected heap.”
还有一种Buffer 称之为Direct buffer，这也是零拷贝的一个方面。
The primary disadvantage of direct buffers is that they’re somewhat more expensive to allocate and release than are heap-based buffers. You may also encounter another drawback if you’re working with legacy code: because the data isn’t on the heap, you may have to make a copy, as shown next.
direct buffers 分配和释放都比heap buffers 花费比较的高。并且direct buffers不能够make a copy。
The third and final pattern uses a composite buffer, which presents an aggregated view of multiple ByteBufs. Here you can add and delete ByteBuf instances as needed, a fea- ture entirely absent from the JDK’s ByteBuffer implementation.
Netty implements this pattern with a subclass of ByteBuf, CompositeByteBuf, which provides a virtual representation of multiple buffers as a single, merged buffer
第三中的类型是混合类型，实现的类型是：CompositeByteBuf。
ByteBuf heapBuf = UnpooledByteBufAllocator.DEFAULT.heapBuffer();
UnpooledByteBufAllocator.DEFAULT.directBuffer();
CompositeByteBuf bytes = UnpooledByteBufAllocator.DEFAULT.compositeBuffer();
heapBuf = PooledByteBufAllocator.DEFAULT.heapBuffer();
bytes = PooledByteBufAllocator.DEFAULT.compositeBuffer() ;
PooledByteBufAllocator.DEFAULT.directBuffer();
CompositeByteBuf may not allow access to a backing array, so accessing the data in a CompositeByteBuf resembles the direct buffer pattern, as shown next.
CompositeByteBuf compBuf = Unpooled.compositeBuffer();
int length = compBuf.readableBytes();
byte[] array = new byte[length];
compBuf.getBytes(compBuf.readerIndex(), array);
handleArray(array, 0, array.length)
Note that Netty optimizes socket I/O operations that employ CompositeByteBuf, elim- inating whenever possible the performance and memory usage penalties that are incurred with the JDK’s buffer implementation.2 This optimization takes place in Netty’s core code and is therefore not exposed, but you should be aware of its impact.
Netty在Socket通信的时候，使用了已经优化的CompositeByteBuf，消除了使用JDK自带的Buffer，可能产生的性能和内存上的问题。
While you may be tempted to call discardReadBytes() frequently to maximize the writable segment, please be aware that this will most likely cause memory copying because the readable bytes (marked CONTENT in the figures) have to be moved to the start of the buffer. We advise doing this only when it’s really needed; for example, when memory is at a premium.
readindex之前的部分，就是已读的部分，已经没有什么用处了，调用discardReadBytes，可以提高buffer的利用率，但是可能会引发内存拷贝的发生，所以谨慎使用。
The method writableBytes() is used here to determine whether there is sufficient space in the buffer.
writableBytes 取得剩余的可写的字节。
The JDK’s InputStream defines the methods mark(int readlimit) and reset(). These are used to mark the current position in the stream to a specified value and to reset the stream to that position, respectively.
mark和reset的作用，标记和恢复。
Similarly, you can set and reposition the ByteBuf readerIndex and writerIndex by calling markReaderIndex(), markWriterIndex(), resetReaderIndex(), and reset- WriterIndex(). These are similar to the InputStream calls, except that there’s no readlimit parameter to specify when the mark becomes invalid.
对应的ByteBuf中也有标记和恢复。
You can also move the indices to specified positions by calling readerIndex(int) or writerIndex(int). Attempting to set either index to an invalid position will cause an IndexOutOfBoundsException.
对特定的标识进行标记
You can set both readerIndex and writerIndex to 0 by calling clear(). Note that this doesn’t clear the contents of memory.
clear 不清理内存的内容。
Calling clear() is much less expensive than discardReadBytes() because it resets the indices without copying any memory.
能使用clear不使用discardReadbytes。
■ duplicate()
■ slice()
■ slice(int, int)
■ Unpooled.unmodifiableBuffer(…)
■ order(ByteOrder)
■ readSlice(int)
This makes a derived buffer inexpensive to create, but it also means that if you modify its contents you are modifying the source instance as well, so beware.
使用上面的方法，能够得到一个副本的buf，但是需要注意，操作的时候是同一个buf。
If you need a true copy of an existing buffer, use copy() or copy(int,int). Unlike a derived buffer, the ByteBuf returned by this call has an independent copy of the data.
如果不想要副本，可以直接的调用copy，直接弄一个新的。
To reduce the overhead of allocating and deallocating memory, Netty implements pooling with the interface ByteBufAllocator, which can be used to allocate instances of any of the ByteBuf varieties we’ve described.
You can obtain a reference to a ByteBufAllocator either from a Channel (each of which can have a distinct instance) or through the ChannelHandlerContext that is bound to a ChannelHandler.
使用ByteBufAllocator分配ByteBuf,ByteBufAllocator的引用可以通过Channel来进行获得。
ByteBufAllocator allocator = channel.alloc();
ByteBufAllocator allocator2 = ctx.alloc();
Netty provides two implementations of ByteBufAllocator: PooledByteBufAllocator and UnpooledByteBufAllocator. The former pools ByteBuf instances to improve per- formance and minimize memory fragmentation. This implementation uses an effi- cient approach to memory allocation known as jemalloc4 that has been adopted by a number of modern OSes. The latter implementation doesn’t pool ByteBuf instances and returns a new instance every time it’s called.
PooledByteBufAllocator和UnpooledByteBufAllocator，亦如类名所示。
There may be situations where you don’t have a reference to a ByteBufAllocator. For this case, Netty provides a utility class called Unpooled, which provides static helper methods to create unpooled ByteBuf instances.
Unpooled 工具类。
Reference counting is a technique for optimizing memory use and performance by releasing the resources held by an object when it is no longer referenced by other objects.
引用计算
Channel channel = ...;
ByteBufAllocator allocator = channel.alloc();
....
ByteBuf buffer = allocator.directBuffer();
assert buffer.refCnt() == 1;
...


{% extends 'base.html' %} {% load staticfiles %} {% block main_content_block %}
Please select an image file to upload and convert to JPEG file.
{{ form.non_field_errors }}
{{ form.file.label_tag }} {{ form.file.help_text }}
{{ form.file.errors }} {{ form.file }}
Note: Processing your file may take some time. Please do not click the button again after submitting this form.


Puzzle 2 part 1
Three light switches (left, middle and right) all start in the "off" position.
You have to switch them all on.
But the circuits are so dodgy that you have to obey certain rules otherwise you’ll cause a short-circuit:
- You can only flick one switch at a time (either on or off)
- You can’t switch the left one on leaving middle and right off.
- You can’t switch the right one on leaving middle and left off.
- If the left and middle switches are on, you can’t also turn the right switch on.
- If the right and middle switches are on, you can’t also turn the left switch on.
Lesson 2 - Draw a Map
Since we don’t have three light switches to hand we have to make a model, or map, of the puzzle
to help us see the solution.
We only have to represent two states for each switch —
“on”
and
“off”,
so we could use a binary notation. Zero for
“off”
and one for
“on”.
The switches all start in the off position, so that’s three zeroes.
000
In order to obey the first three rules there is
only one thing we can do and that is flick the middle switch on.
000
010
We now have a choice.
We can switch on either the left or the right switch.
So on our map we will show both possibilities.
(The third possibility is to turn the middle switch off
again, which would take us back to the beginning
–
a state that is already on the map.)
000
010
110
011
Rule 4 now applies to the left-hand route.
So we can’t turn on the right switch.
Our only choice
(apart from going backwards)
is to turn off the middle switch.
Similarly,
rule 5 applies to the right-hand route.
So we can’t turn on the left switch.
Our only choice is to turn off the middle switch.
000
010
110
011
100
001
On the left-hand route we can only turn on the right switch.
On the right-hand route we can only turn on the left switch.
This brings us to the same point, whichever route we take.
000
010
110
011
100
001
101
And finally we can turn on the middle switch to complete the puzzle.
000
010
110
011
100
001
101
111
Puzzle 2 part 2
This way of mapping the puzzle is fine; but it is not the only way.
Since we have three switches, we can represent them in 3-dimensional space.
We could represent
the left-hand switch on the x-axis
(“on” moves to the right and
“off” moves to the left),
the middle switch on the y-axis
(“on” moves up and
“off” moves down) and
the right-hand switch on the z-axis
(“on” moves away and
“off” moves towards).
Starting with the box that we used for
Puzzle 1 part 2,
apply the rules of this puzzle, which now become;
- You can only move along the edges.
- You can’t go right if you are down and toward.
- You can’t go away if you are down and left.
- If you are right and up, you can’t go away.
- If you are away and up, you can’t go right.
What you should discover is that the two puzzles are identical!


BreastCancerTypeVS
{
"resourceType" : "ValueSet",
"id" : "shr-oncology-BreastCancerTypeVS",
"text" : {
"status" : "generated",
"div" : "

SHR BreastCancerTypeVS ValueSet

Histologic types of breast cancer. Codes are drawn from ICD-O-3. Codes are presented as local codes due to the lack of a ICD-O-3 terminology server available to the FHIR IG publisher.

"
},
"url" : "http://standardhealthrecord.org/shr/oncology/vs/BreastCancerTypeVS",
"identifier" : [
{
"system" : "http://standardhealthrecord.org",
"value" : "shr.oncology.BreastCancerTypeVS"
}
],
"version" : "0.1.0",
"name" : "BreastCancerTypeVS",
"title" : "SHR BreastCancerTypeVS ValueSet",
"status" : "draft",
"date" : "2018-08-22T00:00:00-04:00",
"publisher" : "The MITRE Corporation: Standard Health Record Collaborative",
"contact" : [
{
"telecom" : [
{
"system" : "url",
"value" : "http://standardhealthrecord.org"
}
]
}
],
"description" : "Histologic types of breast cancer. Codes are drawn from ICD-O-3.


×
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Info!
Cooking can only take place if we sign up as a Cleaner, Shopper or Helper
Just eating
you are already joined
I'll clean
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Cook :
Sarah
Date :
4/10/2018
Eating start at :
2:30 O'clock
Cooking start at :
11:15 O'clock
Cooking takes a bout :
3 Hours
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FRC 2022 Robot Code for Team #7464 - ORION
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This file declares some constants for the Logitech F310. More...
Go to the source code of this file.
This file declares some constants for the Logitech F310.
===========================================================================
See: http://team358.org/files/programming/ControlSystem2015-2019/images/Logitech-F310_ControlMapping.pdf
Also see the following for some good information: http://team358.org/files/programming/ControlSystem2015-2019/
COPYRIGHT NOTICES:
Copyright (c) 2019-2022 FRC Team #7464 - ORION. All Rights Reserved. Open Source Software - may be modified and shared by FRC teams. The code must be accompanied by the FRC Team #7464 - ORION BSD license file in the root directory of the project.
Definition in file LogitechF310.h.
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constexpr |
The A button channel
Definition at line 54 of file LogitechF310.h.
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constexpr |
The B button channel
Definition at line 56 of file LogitechF310.h.
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constexpr |
The "Back" button channel
Definition at line 69 of file LogitechF310.h.
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constexpr |
The left rear button channel
Definition at line 64 of file LogitechF310.h.
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constexpr |
The left thumbstick X axis channel
Definition at line 37 of file LogitechF310.h.
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constexpr |
The left thumbstick Y axis channel
Definition at line 39 of file LogitechF310.h.
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constexpr |
The left thumbstick button
Definition at line 74 of file LogitechF310.h.
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constexpr |
The left trigger Y axis channel
Definition at line 42 of file LogitechF310.h.
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constexpr |
The value of the center position of the POV
Definition at line 84 of file LogitechF310.h.
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constexpr |
The value of the East position of the POV
Definition at line 90 of file LogitechF310.h.
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constexpr |
The number ID of this POV on the F310
Definition at line 81 of file LogitechF310.h.
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constexpr |
The value of the North position of the POV
Definition at line 86 of file LogitechF310.h.
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constexpr |
The value of the Northeast position of the POV
Definition at line 88 of file LogitechF310.h.
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constexpr |
The value of the Northwest position of the POV
Definition at line 100 of file LogitechF310.h.
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constexpr |
The value of the South position of the POV
Definition at line 94 of file LogitechF310.h.
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constexpr |
The value of the Southeast position of the POV
Definition at line 92 of file LogitechF310.h.
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constexpr |
The value of the Southwest position of the POV
Definition at line 96 of file LogitechF310.h.
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constexpr |
The value of the West position of the POV
Definition at line 98 of file LogitechF310.h.
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constexpr |
The right rear button channel
Definition at line 66 of file LogitechF310.h.
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constexpr |
The right thumbstick X axis channel
Definition at line 47 of file LogitechF310.h.
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constexpr |
The right thumbstick Y axis channel
Definition at line 49 of file LogitechF310.h.
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constexpr |
The right thumbstick button
Definition at line 76 of file LogitechF310.h.
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constexpr |
The right trigger Y axis channel
Definition at line 44 of file LogitechF310.h.
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constexpr |
The "Start" button channel
Definition at line 71 of file LogitechF310.h.
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constexpr |
The X button channel
Definition at line 59 of file LogitechF310.h.
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constexpr |
The Y button channel
Definition at line 61 of file LogitechF310.h.


---
layout: post
title: JQuery Selectors
---
JQuery Selectors
Selectors are at the heart of JQuery and are part of what makes the library so powerful. John Resig designed JQuery so that developers could leverage their existing knowledge of CSS selectors to to manipulate the DOM.Here are a few common selectors.
JQuery Generic Syntax
A typical JQuery statement follows the syntax
$("selector").method();
//calls the focus method on the DOM element with and id of helloworld
$("#helloworld").focus();
Select an HTML Element or its Descendant
$("element").method();
$("p").css("color","red")
// descendant selectors in the dom
$("element1 element2").method()
Select a direct child element of element1
// matches direct children of element1
$("element1 > elmenet2").method()
//selects paragraph elements that are direct children of the div element
$("div > p ").method()
Universal Selector
//univiersal selector selects all elements
$("*").method()
Elements with specific ids and classes
//Element with a class of classname
$("element.classname").method();
//Element with a id of idname
$("element#idname").method();
Select Elements with a particluar attribute
//selects and element with and attributename of attribute
$("element[attribute]").method();