Re: symbols/codepoints for necessity and possibility in modal logic

What is wrong with using DIAMOND OPERATOR?

A./

On 7/18/2013 8:27 PM, Stephan Stiller wrote:
> Hi all,
>
> Modal logic uses a "box" and a "diamond" (this is how they're
> informally called) as operators (accepting one formula and returning
> another) to denote necessity and possibility, resp. Older texts might
> use the letters L and M (resp). Which Unicode codepoints do modal box
> and diamond correspond to?
>
> According to the charts, it seems like the box is
> ◻ (U+25FB)
> (is this definitive?), but what about the diamond? Unlike what one
> might glean from the charts, ⟠ (U+27E0) is afaiu /not/ normally used
> to denote possibility in the default† sense. Wiki's "List of logic
> symbols" article has something to say about this too, but I'm always
> cautious about information from there.
>
> Stephan
>
> † eg in the sense of "λ𝑥 . ¬◻¬𝑥" with ◻ as used in say the axiom
> schema conventionally named *T* in modal logic
>
>
Received on Fri Jul 19 2013 - 01:37:54 CDT