injective — Mathlib

English

If a function f is surjective, then the Witt vector mapFun f : 𝕎 α → 𝕎 β is surjective.

Русский

Если функция f сюръективна, то WittVector.mapFun f : 𝕎 α → 𝕎 β сюръективно.

LaTeX

$$$\\operatorname{Surjective}(\\mathrm{WittVector.mapFun}\\, f)$$$

Lean4

theorem injective (f : α → β) (hf : Injective f) : Injective (mapFun f : 𝕎 α → 𝕎 β) := fun _ _ h =>
  ext fun n => hf (congr_arg (fun x => coeff x n) h :)

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