🔰二元關係

集合關係 ⟩ 二元關係

  • 二元關係

    • equivalence relations: satisfy reflexivity, symmetry, and transitivity. 💠 example: ab (mod 5)a \equiv b \text{ (mod 5)}

    • partial orders: satisfy reflexivity, antisymmetry, and transitivity. 💠 example: ABA \subseteq B (is a subset of)

    • 全序╱total ordering: satisfy totality, antisymmetry, and transitivity. 💠 example: xyx \le y

    • functions: satisfy a special property called functional dependence. In a function f:AB{\color{orange}f}:A \to B, each element of AA is associated with exactly one element of BB, that is,

      • xA,! yB(x,y)f\forall x \in A, \exists {\color{orange}!} \ y \in B \ni (x,y) \in {\color{orange}f}.

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