English
The shatterer of 𝒜 is the subfamily of all s in the biUnion of 𝒜 with the powerset that are shattered by 𝒜.
Русский
Shatterer(𝒜) — это подсемейство тех \(s \in 𝒜 \uplus \mathcal{P}(\alpha)\), которые расшатаны 𝒜.
LaTeX
$$$\\operatorname{shatterer}(\\mathcal{A}) = \\{ s \\in \\mathcal{A}.biUnion(\\mathcal{P}) \\mid \\mathcal{A}.Shatters s \\}$$$
Lean4
/-- The set family of sets that are shattered by `𝒜`. -/
def shatterer (𝒜 : Finset (Finset α)) : Finset (Finset α) :=
{s ∈ 𝒜.biUnion powerset | 𝒜.Shatters s}