Talk:Turnstile (symbol)

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[edit] comment of Night Gyr 2006-11-15

Nice article, but it needs a source. Also could use a mention of its use in computer science to signify "derivable in a single step," or its meaning of "semantic validity" in formal logic. Mention of double turnstile and possibly a move to Turnstile (symbol) would be in order? Night Gyr (talk/Oy) 19:20, 15 November 2006 (UTC)

Thanks for the comments. The article is just a stub right now; I'll make sure it has sources before the stub tag is removed. I know that there are a lot of uses in computer science, but I am not familiar with all of them. I included just one so far. If someone from CS would like to add more uses, I would be grateful. Moving to Turnstile (symbol) would be OK with me. Semantic validity is a different symbol, \models (corrected). I thought about including that in another section, eventually. CMummert 19:24, 15 November 2006 (UTC)
Ah, my logic prof always used the turnstile with the single vertical. Some clarification would probably be in order. Night Gyr (talk/Oy) 19:45, 15 November 2006 (UTC)
You're right; I typed the symbol \Vdash instead of \models. The second one is the logical validity relation. CMummert 20:29, 15 November 2006 (UTC)

Ah right, it's syntactic validity that has the single horizontal. Night Gyr (talk/Oy) 20:30, 15 November 2006 (UTC)

Right. In all of its uses in math and CS, \vdash always represents some sort of syntactic derivability. CMummert 20:39, 15 November 2006 (UTC)

Can someone please include a description of how this symbol is read when it is the farthest left in a statement? See Generalization (logic) for examples of this usage.129.171.180.147 (talk) 09:45, 13 February 2008 (UTC)

That's the proof theory usage. It means the formula after it can be proved from the stuff before it—i.e. no premises are needed. Algebraist 23:24, 26 April 2008 (UTC)