High Quality Content by WIKIPEDIA articles! In mathematical logic and computer science the symbol vdash has taken the name turnstile because of its resemblance to a typical turnstile if viewed from above. It is also referred to as tee and is often read as "yields" or "proves". The symbol was first used by Gottlob Frege in his 1879 book on logic, Begriffsschrift. In TeX, the turnstile symbol vdash is obtained from the command vdash. In Unicode, the turnstile symbol ? is called right tack and is at code point U+22A2. On a typewriter, a turnstile can be composed from a vertical bar (|) and a dash (-). In LaTeX there is the turnstile package, which issues this sign in many ways, and is capable of putting labels below or above it, in the correct places. The article A Tool for Logicians is a tutorial on using this package.

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