Turnstile (symbol)

Interpretations

• In epistemology, Per Martin-Löf analyzes the symbol thus: "...he combination of Frege's Urteilsstrich, judgement stroke , and Inhaltsstrich, content stroke , came to be called the assertion sign." Frege's notation for a judgement of some content
• In metalogic, the study of formal languages; the turnstile represents syntactic consequence. This is to say, that it shows that one string can be derived from another in a single step, according to the transformation rules of some given formal system. As such, the expression
• In proof theory, the turnstile is used to denote "provability" or "derivability". For example, if is a formal theory and is a particular sentence in the language of the theory then
• In the typed lambda calculus, the turnstile is used to separate typing assumptions from the typing judgment.
• In category theory, a reversed turnstile, as in, is used to indicate that the functor is left adjoint to the functor. More rarely, a turnstile. as in, is used to indicate that the functor is right adjoint to the functor.
• In APL the symbol is called "right tack" and represents the ambivalent right identity function where both ⊢ and ⊢ are. The reversed symbol "⊣" is called "left tack" and represents the analogous left identity where ⊣ is and ⊣ is.
• In combinatorics, means that is a partition of the integer.
• In Hewlett-Packard's HP-41C/CV/CX and HP-42S series of calculators, the symbol is called "Append character" and is used to indicate that the following characters will be appended to the alpha register rather than replacing the existing contents of the register. The symbol is also supported in a modified variant of the HP Roman-8 character set used by other HP calculators.

  Similar graphemes

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