When1: 1920
When2: 1936
Who: Emil Post [Post, Emil]
What: mathematician
Where: USA
works\ Introduction to a General Theory of Elementary Propositions [1920]
Detail: He lived 1897 to 1954. Symbol strings can substitute other symbol strings {Post grammar, Post} {Post machine} [1936], to make formal systems. Start with long symbol string and substitute, using symbol-string precedence rules.
Logic can be three-valued {many-valued logic}. Many-valued logic can use cyclic negation, so next truth-value negates previous one. Such systems include all finite-valued logics. Such logics can represent switching circuits with many inputs and/or outputs.
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Date Modified: 2022.0224