English
Equality x = y is equivalent to atom-le-imp characterizations: for all atoms a, a ≤ x iff a ≤ y.
Русский
Равенство x = y эквивалентно характеристике через атомы: для всех атомов a выполняется a ≤ x ⇔ a ≤ y.
LaTeX
$$$ a = b \\iff \\forall c, IsAtom c \\rightarrow (c \\le a \\iff c \\le b)$$$
Lean4
theorem eq_iff_atom_le_iff {a b : α} : a = b ↔ ∀ c, IsAtom c → (c ≤ a ↔ c ≤ b) :=
by
refine ⟨fun h => by simp [h], fun h => ?_⟩
rw [le_antisymm_iff, le_iff_atom_le_imp, le_iff_atom_le_imp]
simp_all