toEncodable — Mathlib

English

Define decode₂(α) [Encodable α] (n) as decode(n) bound by guard (encode a = n). It returns the preimage if it matches, otherwise none.

Русский

Определение decode₂(α) [Encodable α](n) как связанное с decode(n) и guard (encode a = n); возвращает предобраз, если совпадает, иначе none.

LaTeX

$$$\decode_2(\alpha) [Encodable α] (n) := (\decode n).bind (\text{Option.guard }(\lambda a,\ encode a = n))$$$

Lean4

instance (priority := 100) _root_.IsEmpty.toEncodable [IsEmpty α] : Encodable α :=
  ⟨isEmptyElim, fun _ => none, isEmptyElim⟩

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