| − | The first extension is the ''reflective extension of logical graphs'', or what may be described as the ''cactus language'', after its principal graph-theoretic data structure. It is generated by generalizing the negation operator <math>\texttt{(\_)}\!</math> in a particular manner, treating <math>\texttt{(\_)}\!</math> as the ''[[minimal negation operator]]'' of order 1, and adding another such operator for each integer parameter greater than 1. Taken in series, the minimal negation operators are symbolized by parenthesized argument lists of the following shapes: <math>\texttt{(\_)},\!</math> <math>\texttt{(\_, \_)},\!</math> <math>\texttt{(\_, \_, \_)},\!</math> and so on, where the number of argument slots is the order of the reflective negation operator in question.
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