English
The relation IsExtreme 𝕜 on subsets of E defines a partial order on the power set of E.
Русский
Отношение IsExtreme 𝕜 на подмножествaх E задаёт частичный порядок над множествами-образами E.
LaTeX
$$$\text{IsExtreme}_{𝕜}$ is a partial order on the power set of $E$, i.e. $\forall A,B,C \subseteq E$, A\le B \land B\le C \Rightarrow A\le C$, $A\le A$; and if A\le B and B\le A then A=B.$$$
Lean4
instance : IsPartialOrder (Set E) (IsExtreme 𝕜)
where
refl := IsExtreme.refl 𝕜
trans _ _ _ := IsExtreme.trans
antisymm := IsExtreme.antisymm