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
