Unary Operation/Examples/All Mappings are Unary
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Example of Unary Operation
To a set theorist, all mappings are unary operations.
Proof
Let $\ds \prod_{i \mathop = 1}^n S_i$ be the cartesian product of sets $S_1$ to $S_n$.
Let $f: \ds \prod_{i \mathop = 1}^n S_i \to T$ be a mapping from $\prod_{i \mathop = 1}^n S_i$ to $T$.
Thus:
- $f \subseteq \paren {S_1 \times S_2 \times \dotsb \times S_n} \times T$
Hence to consider $f$ as a unary operation, one would consider $\ds \prod_{i \mathop = 1}^n S_i$ as:
- a set whose elements are ordered $n$-tuples
as opposed to:
- an $n$-dimensional cartesian product of sets.
A set theorist, to a certain level of approximation, considers a set to be an aggregation of any objects.
Hence a set of ordered $n$-tuples is a convenient way to regard the domain of $f$.
$\blacksquare$
Sources
- 1993: Keith Devlin: The Joy of Sets: Fundamentals of Contemporary Set Theory (2nd ed.) ... (previous) ... (next): $\S 1$: Naive Set Theory: $\S 1.6$: Functions: Exercise $1.6.1$