Bracket
From Wikinfo
- See parenthesis for an account of the rhetorical concept from which the name of the punctuation mark is derived.
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In writing
Brackets are punctuation marks, used in pairs to set apart or interject text within other text. Types of brackets include parentheses�(�), (the singular is parenthesis) square brackets�[�], braces�{�}, and angle brackets 〈�〉. All these forms may be used according to typographical conventions that may vary from publication to publication. Some typical uses follow.
Types of brackets
Parentheses ()
Parentheses are used to contain parenthetical (or optional, additional) material in a sentence that could be removed without destroying the meaning of the main text. For example, "George Washington (the father of his country) was not the wooden figure with wooden teeth that many think him." Indeed, such an interjection is called a parenthesis, and may also be set off with dashes or commas.
Parentheses may be used to add supplementary information, such as "Sen. Kennedy (D., Massachusetts) spoke at length."
Parentheses may also be nested (with one set inside another set (but this is not commonly used in formal writing)). Often square brackets will be used for the inner set of parentheses.
Any punctuation inside parentheses or other brackets is independent from the rest of the text: "Mrs. Pennyfarthing (What? Yes, that was her name!) was my landlady."
In mathematics, parentheses are used to signify a different precedence of operators. For example, 2�+�3�נ4 would be 14, since the multiplication is done before the addition. (2�+�3)�נ4 is 24, because the parentheses override normal precedence, causing the addition to be done first. They are also used to set apart the arguments to mathematical functions. For example, f(x) is the function f applied to the variable x.
Square brackets []
Square brackets are used to enclose explanatory or missing [...] material, especially in quoted text. For example, "I appreciate it [the honor], but I must refuse." Or, "The future of psionics [See definition] is in doubt."
The bracketed expression [sic] (Latin for "thus") is used to indicate errors that are "thus in the original"; a bracketed ellipsis [...] is used to indicate deleted material; bracketed comments are used to indicate when original text has been modified: "I'd like to thank [several unimportant people] and my parentals [sic] for their love, tolerance [...] and assistance [italics added]."
Square brackets are also often used as parentheses within parentheses.
Braces {}
Braces are sometimes used in prose to indicate a series of equal choices: "Select your animal {goat, sheep, cow, horse} and follow me." They are used in specialized ways in poetry and music (to mark repeats or joined lines). In mathematics they are used to delimit sets.
In computer programming, braces sometime denote the beginning and ending of a sequence of statements.
Angle brackets 〈〉
Angle brackets (〈,�〉) are often used to enclose highlighted material. Some dictionaries use angle brackets to enclose short excerpts illustrating the usage of words. True angle brackets are not available on a typical computer keyboard, so the "less than" and "greater than" symbols are used instead (<,�>). These are often loosely referred to as "angle brackets" when used in this way. For example, the symbols <�and�> are often used to set apart URLs in text, such as "I found it in Wikipedia <www.wikipedia.org>."
Single and double angle brackets (〈〈,�〉〉) or pairs of the appropriate comparison operators (<<,�>>) are sometimes used instead of guillemets when the proper glyphs are not available.
The mathematical or logical symbols for greater-than�(>) and less-than�(<), when used as such, are not punctuation marks.
Alternate names for brackets
Parentheses are sometimes called round brackets, curved brackets or, colloquially, parens, or fingernails. John Lennard (in "The exploitation of parentheses in English printed verse") usefully coined the term lunula to refer specifically to the opening curved bracket, the closing curved bracket and the textual contents between.
Square brackets are called crochets in Britain.
Braces are often called curly brackets. Presumably due to the similarity of the word "brace" and "bracket", many people apparently (and incorrectly) believe that "brace" is a synonym for "bracket". Therefore, when it is necessary to avoid any possibility of confusion, e.g., in computer programming, it may be best to use the term "curly bracket" rather than "brace". However, general usage in English favors the latter form. The term curly braces is redundant since that is the only kind of braces there are.
Brackets in computing
- Opening and closing parentheses correspond to Unicode and ASCII characters 40 and 41, or 0x0028 and 0x0029, respectively.
- For square brackets corresponding values are 91 and 93, or 0x005B and 0x005D.
- For braces, 123 and 125, or 0x007B and 0x007D.
- True angle brackets are available in Unicode at code points 9001 and 9002, or 0x2329 and 0x232A. The less than and greater than symbols can be found in both Unicode and ASCII at code points 60 and 62 respectively, or 0x003C and 0x003E.
Also, in many programming languages:
- "(" and ")" are used to contain the arguments to functions: substring($val,10,1). Parentheses are so ubiquitous in the Lisp programming language that the name is said to be an acronym for "Lots of Irritating Superfluous Parentheses". They may also be used to indicate the start and end of lists.
- "[" and "]" are used to define elements in an array: $animals["goat"].
- "{" and "}" are used to define the beginning and ending of blocks of code. To complicate things, in the Pascal programming language, "{" and "}" define the beginning and ending of comments.
- "<" and ">" are used in SGML (and other formats based on SGML, such as HTML and XML), to enclose code tags.
'Mismatched' brackets [)
The notation [a, c) is used to indicate a sequence starting at a, but ending at the element before c (i.e. c is not a part of the sequence.) This is used in mathematical notation, and in some computer programming languages.
Brackets in Wikipedia
In the Wikipedia editor, and some other Wikis, square brackets are used to link to external sources; doubled square brackets are used to link to pages within Wikipedia.
In Sports
- Tournament brackets, such as those used in sports tournaments (tennis tournaments, 9-ball tournaments, or March Madness and other NCAA tournaments).
In mechanics and structures
A bracket may be an inverted "L" shape, such as is usually used to hold up a shelf or a rafter extension and diagonal brace supporting an overhanging roof over a gable. Fancy brackets used in furniture and mantlepieces are sometimes called corbels.
See also
References
- Adapted from the Wikipedia article, "Bracket" http://en.wikipedia.org/wiki/Bracket, used under the GNU Free Documentation License
