| | | |
|---|---|
Vertical bar | |
| In Unicode | U+007C |VERTICAL LINE (|, |, |) |
| Related | |
| See also | U+00A6 ¦BROKEN BAR (¦) U+2016 ‖DOUBLE VERTICAL LINE (‖, ‖) |
Thevertical bar,|, is aglyph with various uses inmathematics,computing, andtypography. It has many names, often related to particular meanings:Sheffer stroke (inlogic),pipe,bar,or (literally, the word "or"),vbar, and others.[1]
The vertical bar is used as amathematical symbol in numerous ways.If used as a pair of brackets, it suggests the notion of the word "size". These are:
Likewise, the vertical bar is also used singly in many different ways:
Thedouble vertical bar,, is also employed in mathematics.
In LaTeXmathematical mode, the ASCII vertical bar produces a vertical line, and\| creates a double vertical line (a | b \| c is set as). This has different spacing from\mid and\parallel, which arerelational operators:a \mid b \parallel c is set as. See below aboutLaTeX in text mode.
In chemistry, the vertical line is used incell notation of electrochemical cells.
Example,
Zn | Zn2+ || Cu2+ | Cu
Single vertical lines show components of the cell which do not mix, usually being in different phases. The double vertical line ( || ) is used to represent salt bridge; which is used to allow free moving ions to move.
The vertical bar is used inbra–ket notation inquantum physics. Examples:
Apipe is aninter-process communication mechanism originating inUnix, which directs the output (standard out and, optionally, standard error) of one process to the input (standard in) of another. In this way, a series of commands can be "piped" together, giving users the ability to quickly perform complex multi-stage processing from thecommand line or as part of aUnix shell script ("bash file"). In mostUnix shells (command interpreters), this is represented by the vertical bar character. For example:
grep -i 'blair' filename.log |more
where the output from thegrep process (all lines containing 'blair') is piped to themore process (which allows a command line user to read through results one page at a time).
The same "pipe" feature is also found in later versions ofDOS and Microsoft Windows.
This usage has led to the character itself being called "pipe".
In Windows the shortcut isAltGr+179.[7]
In many programming languages, the vertical bar is used to designate thelogic operationor, eitherbitwiseor orlogicalor.
Specifically, inC and other languages followingC syntax conventions, such asC++,Perl,Java andC#,a | b denotes abitwiseor; whereas a double vertical bara || b denotes a (short-circuited)logicalor. Since the character was originally not available in allcode pages and keyboard layouts,ANSI C can transcribe it in form of thetrigraph??!, which, outside string literals, is equivalent to the| character.
Inregular expression syntax, the vertical bar again indicates logicalor (alternation). For example: the Unix commandgrep -E 'fu|bar' matches lines containing 'fu' or 'bar'.
The double vertical bar operator "||" denotesstringconcatenation inPL/I,REXX,ooRexx, standardANSI SQL, and theoretical computer science (particularlycryptography).
Although not as common as commas or tabs, the vertical bar can be used as adelimiter in aflat file. Examples of apipe-delimited standard data format areLEDES 1998B andHL7. It is frequently used because vertical bars are typically uncommon in the data itself.
Similarly, the vertical bar may see use as a delimiter forregular expression operations (e.g. insed). This is useful when the regular expression contains instances of the more common forward slash (/) delimiter; using a vertical bar eliminates the need to escape all instances of the forward slash. However, this makes the bar unusable as the regular expression "alternative" operator.
InBackus–Naur form, an expression consists of sequences of symbols and/or sequences separated by '|', indicating achoice, the whole being a possible substitution for the symbol on the left.
<personal-name>::=<name> |<initial>
In calculi of communicating processes (likepi-calculus), the vertical bar is used to indicate that processes execute in parallel.
The pipe inAPL is the modulo orresidue function between two operands and the absolute value function next to one operand.
The vertical bar is used for list comprehensions in some functional languages, e.g.Haskell andErlang. Compareset-builder notation.
The vertical bar is used as a special character inlightweight markup languages, notablyMediaWiki'sWikitext (in the templates and internal links).
In LaTeX text mode, the vertical bar produces anem dash (—). The\textbar command can be used to produce a vertical bar.
In theKhoisan languages and theInternational Phonetic Alphabet, the vertical bar is used to write thedental click (ǀ). A double vertical bar is used to write thealveolar lateral click (ǁ). Since these are technically letters, they have their ownUnicode code points in theLatin Extended-B range: U+01C0 for the single bar and U+01C1 for the double bar.
SomeNorthwest andNortheast Caucasian languages written in theCyrillic script have a vertical bar calledpalochka (Russian:палочка,lit. 'little stick'), indicating the preceding consonant is anejective.
Longer single and double vertical bars are used to markprosodic boundaries in the IPA.
In medieval European manuscripts, a single vertical bar was a common variant of thevirgula/ used as acomma,[8] orcaesura mark.[8]
InSanskrit and otherIndian languages, a single vertical mark, ।, called adanda, has a similar function as a period (full stop). Two bars, ॥, (a 'double danda') is the equivalent of apilcrow in marking the end of astanza, paragraph or section. The danda has its own Unicode code point,U+0964 ।DEVANAGARI DANDA; as does the double danda:U+0965 ॥DEVANAGARI DOUBLE DANDA.
A double vertical bar⟨||⟩ or⟨‖⟩[citation needed] is the standardcaesura mark in Englishliterary criticism and analysis. It marks the strong break orcaesura common to many forms ofpoetry, particularlyOld English verse. It is also traditionally used to mark the division between lines of verse printed as prose (the style preferred byOxford University Press), though it is now often replaced by theforward slash.[citation needed]
In theGeneva Bible and early printings of theKing James Version, a double vertical bar is used to markmargin notes that contain an alternative translation from the original text. These margin notes always begin with the conjunction "Or". In later printings of the King James Version, the double vertical bar is irregularly used to mark any comment in the margins.
A double vertical bar symbol may be used to call out afootnote. (The traditional order of these symbols in English is*,†,‡,§, ‖,¶, so its use is very rare; in modern usage, numbers and letters are preferred forendnotes and footnotes.[9])
In music, when writing chord sheets, single vertical bars associated with a colon (|: A / / / :|) represents the beginning and end of a section (e.g. Intro, Interlude, Verse, Chorus) of music.[citation needed] Single bars can also represent the beginning and end of measures (|: A / / / | D / / / | E / / / :|). A double vertical bar associated with a colon can represent the repeat of a given section (||: A / / / :|| - play twice).[citation needed]
Many early video terminals anddot-matrix printers rendered the vertical bar character as theallographbroken bar¦. This may have been to distinguish the character from the lower-case 'L' and the upper-case 'I' on these limited-resolution devices, and to make a vertical line of them look more like a horizontal line of dashes. It was also (briefly) part of theASCII standard.
An initial draft for a 7-bit character set that was published by the X3.2 subcommittee for Coded Character Sets and Data Format on June 8, 1961, was the first to include the vertical bar in a standard set. The bar was intended to be used as the representation for thelogical OR symbol.[10] A subsequent draft on May 12, 1966, places the vertical bar in column 7 alongside regional entry codepoints, and formed the basis for the original draft proposal used by theInternational Standards Organisation.[10] This draft received opposition from theIBM user groupSHARE, with its chairman, H. W. Nelson, writing a letter to theAmerican Standards Association titled "The Proposed revised American Standard Code for Information Interchange does NOT meet the needs of computer programmers!"; in this letter, he argues that no characters within the international subset designated at columns 2-5 of the character set would be able to adequately represent logical OR andlogical NOT in languages such as IBM'sPL/I universally on all platforms.[11] As a compromise, a requirement was introduced where theexclamation mark (!) andcircumflex (^) would display as logical OR (|) and logical NOT (¬) respectively in use cases such as programming, while outside of these use cases they would represent their original typographic symbols:
"It may be desirable to employ distinctive styling to facilitate their use for specific purposes as, for example, to stylize the graphics in code positions 2/1 and 5/14 to those frequently associated with logical OR (|) and logical NOT (¬) respectively."
— X3.2 document X3.2/475[12]
The original vertical bar encoded at 0x7C in the original May 12, 1966 draft was then broken as¦, so it could not be confused with the unbroken logical OR. In the 1967 revision of ASCII, along with the equivalent ISO 464 code published the same year, the code point was defined to be a broken vertical bar, and the exclamation mark character was allowed to be rendered as a solid vertical bar.[13][14] However, the 1977 revision (ANSI X.3-1977) undid the changes made in the 1967 revision, enforcing that the circumflex could no longer be stylised as a logical NOT symbol, the exclamation mark likewise no longer allowing stylisation as a vertical bar, and defining the code point originally set to the broken bar as a solid vertical bar instead;[13] the same changes were also reverted in ISO 646-1973 published four years prior.
Some variants ofEBCDIC included both versions of the character as different code points. The broad implementation of theextended ASCIIISO/IEC 8859 series in the 1990s also made a distinction between the two forms. This was preserved in Unicode as a separate character at U+00A6BROKEN BAR (the term "parted rule" is used sometimes in Unicode documentation). Some fonts draw the characters the same (both are solid vertical bars, or both are broken vertical bars).[15][failed verification]
Many keyboards with US, US-International, and GermanQWERTZ layout display the broken bar on a keycap even though the solid vertical bar character is produced. This is a legacy of keyboards manufactured during the 1980s and 1990s forIBM PC compatible computers, as the IBM PC continued to display the glyph for the broken bar at codepoint 7C on displays fromMDA (1981) toVGA (1987) despite the changes made to ASCII in 1977. The UK/Ireland keyboard has both symbols engraved: the broken bar is given as analternate graphic on the "grave" (backtick) key; the solid bar is on thebackslash key.
The broken bar character can be typed (depending on the layout) asAltGr+` orAltGr+6 orAltGr+⇧ Shift+\ on Windows andCompose!^ on Linux. It can be inserted into HTML as¦
The broken bar does not appear to have any clearly identified uses distinct from those of the vertical bar.[16] In non-computing use — for example in mathematics, physics and general typography — the broken bar is not an acceptable substitute for the vertical bar. In some dictionaries, the broken bar is used to mark stress that may be either primary or secondary:[¦ba] covers the pronunciations[ˈba] and[ˌba].[17]
These glyphs are encoded in Unicode as follows:
| Code pages, ASCII, ISO/IEC, EBCDIC, Shift-JIS, etc. | Vertical bar (|) | Broken bar (¦) |
|---|---|---|
| ASCII, CP437,CP667,CP720,CP737,CP790,CP819,CP852,CP855,CP860,CP861,CP862,CP865,CP866,CP867,CP869,CP872,CP895,CP932,CP991 | 124 (7Ch) | none |
| CP775 | 167 (A7h) | |
| CP850,CP857,CP858 | 221 (DDh) | |
| CP863 | 160 (A0h) | |
| CP864 | 219 (DBh) | |
| ISO/IEC 8859-1,-7,-8,-9,-13, CP1250,CP1251,CP1252,CP1253,CP1254,CP1255,CP1256,CP1257,CP1258 | 166 (A6h) | |
| ISO/IEC 8859-2,-3,-4,-5,-6,-10,-11,-14,-15,-16 | none | |
| EBCDIC CCSID 37 | 79 (4Fh) | 106 (6Ah) |
| EBCDIC CCSID 500 | 187 (BBh) | |
| JIS X 0208,JIS X 0213 | Men-ku-ten 1-01-35 (7-bit: 2143h;Shift JIS: 8162h;EUC: A1C3h)[a] | none |
But beyond the ... double dagger, this order is not familiar to most readers, and never was.
