Singleton

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Generally, a singleton is something which exists alone in some way. The word is used in several different areas:

  • In mathematics, a singleton is a set with exactly one element. See singleton (mathematics).
  • In computer programming, a singleton is a common design pattern. It refers to a class which is not meant to be freely instantiated, but have only one instance. See Singleton pattern. A singleton is also a variable that is only used once in a program, usually indicating a programming mistake. See singleton variable.
  • In variable-width encoding schemes for computer character sets, a singleton is a character encoded with one unit, as opposed to characters encoded with multiple-unit sequences.
  • In Unicode, a singleton is a character the decomposition of which consists of a single character (e.g. the "ohm sign" (Ω) is decomposed as the "Greek capital letter omega" (Ω)).
  • A singleton is a baby that is not a twin or other multiple birth.
  • In the wake of the popularity of the novel and movie Bridget Jones's Diary, the word has also become popular as a (self-)description of individuals without romantic partners, particularly applied to women in their thirties. There is an undertone to this use of ignoring societal pressures towards marriage and motherhood.
  • In trick-taking games where suit is important, such as contract bridge and Hearts, if a hand contains only one card of a particular suit, that card is called a singleton. Certain bidding systems (notably Acol) add notional value to the hand for a short suit of this type since it exposes the possibility of trumping. Similarly, holding a "singleton Queen" (of Spades) in Hearts is a very disadvantageous position.
  • In Whisky singleton describes the last cask or charge of a Whisky.
  • In espionage, a singleton is an intelligence officer who works alone, in that he has no supporting network.
  • In science fiction stories involving multiple parallel universes, a singleton is a person, place, or thing that exists in only one reality, regardless of how alike said realities might be otherwise. This is often used as a rationale for travel between those worlds.
  • Singleton is the title of a short story by Greg Egan.
  • In conformal field theory, see singleton field.
  • In air combat manoeuvering, a singleton is a radar or visual contact confirmed to be a single aircraft.
  • In coding theory, see Singleton bound.
  • In XML (and its subsets such as XHTML) coding, refers to an empty tag, or self-closing tag, such as <br /> or <img ... />.

[edit] Places called Singleton

In Australia:

In the United Kingdom:

In the United States

  • Singleton's in Ludlow, Vermont, a general store

[edit] People named Singleton

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