Cyclic negation

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In logic, cyclic negation is (assuming that the truth values are linearly ordered) a unary truth function that takes a truth value n and returns n-1 as value if n isn't the lowest value; otherwise it returns the highest value. For example, let (i) be the set of truth values be {0,1,2}, (ii) '~' denote negation, and (iii) p be a variable ranging over truth values. Thus if p=0 then ~p=2; and if p=1 then ~p=0.

It was originally introduced by the logician and mathematician Emil Post.