# Anyone encounter these Logic symbols?

These diagrams are equivalent representations of the 2-ary boolean functions. What are the symbols used in the top left diagram?

(Source: wikicommons user mate2code)

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I'm fairly certain that the symbols in the upper left diagram are not standard in the field of symbolic logic. – Trevor Wilson Mar 21 '13 at 1:52
I'm not even going to follow your link, but I predict it's an illustration created by user "Lipedia". He (or she) is somewhat infamous for creating extremely confusing and unclear (though sometimes visually beautiful) "visualizations" of a range of discrete math topics. There's a good chance he invented some of this symbolism himself and nobody else uses it. – Henning Makholm Mar 21 '13 at 1:55
It looks like Lipedia's account is now called Mate2code. I don't think he's a troll; he's way too prolific and lavishes too much loving care on his illustrations for that. But he also has a real problem with understanding which kind of diagrams will be any use for a reader. – Henning Makholm Mar 21 '13 at 2:01
It appears to be what he calls Nibble Shorthands, which represent nibbles, I guess. You could probably ask him how he came up with them and why their shapes make sense, I would bet he has a beautiful answer. – Alfonso Fernandez Mar 21 '13 at 2:14
@AlfonsoFernandez: That's as close to an answer as we'll ever get, I think. (I tend to use the symbols 0123456789ABCDEF to represent nibbles, but I'm just a freak, I suppose). – Henning Makholm Mar 21 '13 at 2:20

mate2code calls them nibble shorthands, and they simply represent all possible nibbles (four digit binary strings, more commonly represented by the numbers $0$ to $15$ or by the hexadecimal digits 0 to F), in an order which can be seen here (by interpreting the red dots under each symbol as $1$'s and the white dots as $0$'s).