Vertical bar
What is this site? It is generaly simplier version of wikipedia. You will find there selected articles. Enjoy!
- Note: "broken bar" and the glyph "¦" redirect here.
The vertical bar (|) is a character with various uses in mathematics, where it can be used to represent absolute value, among others; in computing and programming; and in general typography, as a divider not unlike the interpunct. It may be called by various other names including the pipe (by the Unix community, referring to the I/O pipeline construct), Sheffer stroke (by computer or mathematic logicians), verti-bar, vbar, stick, vertical line, vertical slash, think colon, or divider line by others.
The (¦), also termed "parted rule" in Unicode documentation, is a separate character, but due to historical confusion between the two, computer keyboards and displays may not clearly or consistently differentiate them. The typical keyboard layout used in the United Kingdom features separate keys for vertical bar and broken bar; however, typically on Windows PCs the vertical bar key produces a broken-bar symbol and vice versa. North American keyboards typically have a key bearing a broken-bar symbol, which produces a vertical bar. In the default console font on PC systems, the glyph used for the vertical bar character looks exactly like a broken bar.
The broken bar does not appear to have any clearly identified uses distinct from the vertical bar. The examples in this article all use the vertical bar, but in actual use in some computing environments (for example, in use as a DOS pipe character), a broken bar may be displayed instead. In non-computing use — for example in mathematics, physics and general typography — the broken bar is not an acceptable substitute for the vertical bar.
The URL encoding of the pipe is %7C.
Contents |
Usage
Mathematics
The vertical bar is used as a mathematical symbol in
- absolute value: | x | , read "the absolute value of x".
- norms:
, read "the norm of x sub one, x sub two"; though Unicode also provides a special double vertical line symbol U+2016: ‖x‖ - set-builder notation: {x | x < 2}, read "the set of x such that x is less than two". Often a colon ':' is used instead of a vertical bar.
- cardinality: | S | , read "the cardinality of the set S".
- conditional probability: P(X | Y), read "the probability of X given Y".
- divisibility: a | b, read "a divides b", though Unicode also provides special ‘divides’ and ‘does not divide’ symbols (U+2223 and U+2224: ∣, ∤)
- the Sheffer stroke in logic: a | b, read "a nand b".
- evaluate: a + 3 | a = 4, read "a plus 3 evaluated for when a equals 4", or 4 + 3 = 7.
- evaluate (subscript notation): f(x) | x = 4, read "f of x evaluated at x equals 4"
- restriction:
denotes a restriction of function f where it is defined over a domain which is a superset of A.
Physics
The vertical bar is used in bra-ket notation in quantum physics. Examples:
— The quantum mechanical state "ψ".
— The dual state corresponding to the state above.
— The inner product of states ψ and ρ.
Language
 |
This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2010) |
In English, the vertical bar is used as punctuation for sarcastic or satirical sentences. This development is fairly new and likely derived due to the realities of currently existing linguistics. The | is one of the few symbols which is both present on the keyboard most commonly used in America, the qwerty, and nearly every English symbol bank as well as being free of other uses in English Linguistics. The | fits well with the other punctuation already in use by the English language and so its use was an obvious result as individuals sought a way to clarify what internet posts and text messages were intended sarcastically. Many symbols were proposed and even used prior to the vertical bar but all these symbols diverged too much from the current English grammar paradigm and were quickly swept aside. The vertical bar is used identically to the other punctuations, replacing them at the end of the sentence, excepting the case of satirical or sarcastic questions in which the vertical bar follows the question mark, such as "?|". The Use of | has been attributed to its’ earlier use in mathematics to denote Absolute value. Whereas two of the vertical bars would constitute the interpretation of the sentence within to be completely positive regardless of what was written. Such as: “|Aren’t you just the smartest?|” Which, if taken at absolute value, would seem to imply that the person being referenced was actually incredibly smart. Now take the first vertical bar away: “Aren’t you just the smartest?|” Here the sentence lacks an absolute value, but because it is finished with the vertical bar, which is half of an absolute value, the sentence would represent partial value of the statement while allowing for peripheral negativity. The use of just one of vertical bars allows for the sentence to relay a possibly negative message but to be annotated, at least in part, positively. Sarcasm and satire, after all, are a form of jest and so, even when intended to bestow some critique, must be interpreted with some level of positive humor.
Marks like the Snark mark and Sarcmark, as well as others suggested, such as sarcastic sentences being put between < > or the use of the ~ symbol by itself, seem to think that because sarcasm is more expressive than common statements that the mark which delineates sarcasm must be equally expressive. However, there is nothing about the question mark which is inherently tied to a question, or exclamatory about an exclamation point. The symbol is not definitive of the connotation of the sentence beside that we have claimed them to be; the | claims to indicate sarcasm, and so it does. The socially accepted used of the question mark is to signify a question, and so we used it. Sarcasm in text form is a fairly new ball game that has arisen in the technological age and the mark that will define it has yet to reach such a social consensus but the | seems to be leading the way.
Computing
Pipe
A pipe is an inter-process communication mechanism originating in Unix which allows the output (standard out and, optionally, standard error) of one process to be used as input (standard in) to another. In this way, a series of commands can be "piped" together, giving users the ability to quickly perform complex multi-stage processing from the command line or as part of a Unix shell script ("batch file"). In most Unix shells (command interpreters), this is represented by the vertical bar character. For example:
where the output from the "egrep" process is piped to the "more" process.
The same "pipe" feature is also found in later versions of DOS and Microsoft Windows.
Disjunction
In many programming languages, the vertical bar is used to designate the logic operation or, either bitwise or or logical or.
Specifically, in C and other languages following C syntax conventions, such as C++, Perl, Java and C#, (a | b) denotes a bitwise or; whilst a double vertical bar (a || b) denotes a (short-circuited) logical or.
In regular expression syntax, the vertical bar again indicates logical or. For example: the Unix command grep -E 'foo|bar' matches lines containing 'foo' or 'bar'.
Concatenation
In PL/I and certain dialects of SQL, the operator "||" denotes string concatenation.
Delimiter
Although not as common as commas or tabs, the vertical bar can be used as a delimiter in a flat file. An example of a pipe-delimited standard data format is LEDES 1998B.
Backus-Naur form
In Backus-Naur form, an expression consists of sequences of symbols and/or sequences separated by '|', indicating a choice, the whole being a possible substitution for the symbol on the left.
- <personal-name> ::= <name> | <initial>
Concurrency operator
In calculi of communicating processes (like pi-calculus), the vertical bar is used to indicate that processes execute in parallel.
List comprehensions
The vertical bar is used for list comprehensions in some functional languages, e. g. Haskell and Erlang. Compare set-builder notation.
Wikipedia
Phonetics and orthography
In the Khoisan languages and the International Phonetic Alphabet, the vertical bar is used to write the dental click (ǀ). A double vertical bar is used to write the alveolar lateral click (ǁ). Since these are technically letters, they have their own Unicode code points in the Latin Extended-B range: U+01C0 for the single bar and U+01C1 for the double bar. Longer single and double vertical bars are used to mark prosodic boundaries in the IPA.
Encoding
The vertical bar ("|") is at position 124 (decimal) in the ASCII character set. The broken bar ("¦") is not part of ASCII but is a separate character that appeared (along with vertical bar) first in the EBCDIC family of character sets, and was copied from there into ISO 8859-1 and Unicode.
The typical computer keyboard used in the United Kingdom features separate keys for "vertical bar" and "broken bar", even though "broken bar" has hardly any practical application. Some keyboard drivers map the broken bar key to the vertical bar, and the vertical bar key, shared with the grave accent (`), generates the broken bar when pressed in combination with AltGr.
In common character maps
Additional related Unicode characters:
- Double vertical line ('‖'): U+2016
- Latin letter dental click ('ǀ'): U+01C0
- Latin letter lateral click ('ǁ'): U+01C1
- Various box-drawing characters at U+2500 to U+257F
References
- ^ http://www.jimprice.com/jim-asc.shtml#extended
- ^ http://www.cs.tut.fi/~jkorpela/latin1/3.html#A6
- ^ http://www.blooberry.com/indexdot/html/topics/urlencoding.htm
- ^ http://thesnark.org/history/
- ^ http://www.thestar.com/living/article/751364--hitting-the-mark-with-sarcasm