String

A String is a Finite Sequence of String Symbols (from an Alphabet).

• AKA: Symbol String, Finite String.
• Context:
  • It can have an Empty String it if has Zero Members.
  • It can be
    • a Formal String if it satisfies a Formal Language.
    • a Linguistic Expression in a Natural Language.
  • It can, based on its String Length, range from:
    • being a Short String,
    • to being a Long String.
  • It can be compared against another String with a String Distance Function.
  • It is an Abstract Entity.
  • It can be represented by a List.
• Example(s):
  • [A]
  • [12]
  • [1 milllllion monkeys typing.]
  • [10fa23]
  • ([I] [bought] [a] [real time] [operating system]), a Terminal Word String.
  • ([日文] [章魚] [怎麼] [說]), a Terminal Word String.
• Counter-Example(s):
  • an Infinite Sequence, such as 1,1,2,3,5,8,...
• See: Alphabet, String Kernel, Text, Sequence.

References

2009

• (Wikipedia, 2009) http://en.wikipedia.org/wiki/String_(computer_science)
  • In computer programming and some branches of mathematics, a string is an ordered sequence of symbols. These symbols are chosen from a predetermined set or alphabet.
  • In computer programming, a string is generally understood as a data type storing a sequence of data values, usually bytes, in which elements usually stand for characters according to a character encoding, which differentiates it from the more general array data type. In this context, the terms binary string and byte string are used to suggest strings in which the stored data does not (necessarily) represent text.
  • A variable declared to have a string data type usually causes storage to be allocated in memory that is capable of holding some predetermined number of symbols.
  • When a string appears literally in source code, it is known as a string literal and has a representation that denotes it as such.
• http://www.csee.umbc.edu/help/theory/lang_def.shtml
  • String also called a Word
    • A finite sequence of symbols from an alphabet.
    • 01110 and 111 are strings from the alphabet B above.
    • aaabccc and b are strings from the alphabet C above.
    • A null string is a string with no symbols, usually denoted by epsilon.
    • The null string has length zero.
    • The null string is usually denoted epsilon.
    • Vertical bars around a string indicate the length of a string expressed as a natural number. For example |00100| = 5, |aab| = 3, | epsilon | = 0

2007

• (Kakkonen, 2007) => Tuomo Kakkonen. (2007). "Framework and Resources for Natural Language Evaluation. Academic Dissertation. University of Joensuu.
  • Definition 3-1. Symbol, terminal and alphabet.
    • A symbol is a distinguishable character, such as “a”, “b” or “c”.
    • Any permissible sequence of symbols is called a terminal (also referred to as a word).
    • A finite, nonempty set ∑ of terminals is called an alphabet.
  • Definition 3-2. String and sets of strings.
    • Let Σ be an alphabet.
    • A finite sequence of symbols S=(x1 x2… xn), n≥0, x∈Σ is called a string in alphabet Σ.
    • The length |S| of string S is n.
    • The empty string is the sequence of length 0; written ε.
    • Σ* is the set of all strings in Σ.
    • In addition, Σ+ = Σ*- {ε}.
  • Definition 3-3. Language and sentence.
    • Let Σ be an alphabet.
    • Any subset L of Σ* is called a language over alphabet Σ.
    • Sequence δ = (α1 α2 … αn), where αi ∈ L∀i, 1≤i≤n, n ∈ natural numbers, is called a sentence in language L.
  • A language follows the rules of a given grammar and is represented by using a particular grammar formalism.

1996

• (Wall & al, 1996) => Larry Wall, Tom Christiansen, and Randal L. Schwartz. (1996). "Programming Perl, 2nd edition." O'Reilly. ISBN 1565921496 (alternate, search)
  • string: A sequence of characters such as "He said !@#*&%@#*?\n." A string does not have to be entirely printable.