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structure

RecognitionAutomorphism

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module
IndisputableMonolith.RecogGeom.Symmetry
domain
RecogGeom
line
148 · github
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IndisputableMonolith.RecogGeom.Symmetry on GitHub at line 148.

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All declarations in this module, on Recognition.

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 145/-! ## Bijective Symmetries (Automorphisms) -/
 146
 147/-- A bijective recognition-preserving map (automorphism) -/
 148structure RecognitionAutomorphism (r : Recognizer C E) extends RecognitionPreservingMap r where
 149  /-- The inverse function -/
 150  invFun : C → C
 151  /-- Left inverse property -/
 152  left_inv : ∀ c, invFun (toFun c) = c
 153  /-- Right inverse property -/
 154  right_inv : ∀ c, toFun (invFun c) = c
 155
 156/-- The inverse of an automorphism preserves events -/
 157theorem RecognitionAutomorphism.inv_preserves_event (T : RecognitionAutomorphism r) (c : C) :
 158    r.R (T.invFun c) = r.R c := by
 159  have h := T.preserves_event (T.invFun c)
 160  rw [T.right_inv] at h
 161  exact h.symm
 162
 163/-- The inverse of an automorphism is an automorphism -/
 164def RecognitionAutomorphism.inv (T : RecognitionAutomorphism r) : RecognitionAutomorphism r where
 165  toFun := T.invFun
 166  preserves_event := T.inv_preserves_event
 167  invFun := T.toFun
 168  left_inv := T.right_inv
 169  right_inv := T.left_inv
 170
 171/-- The identity automorphism -/
 172def idAutomorphism : RecognitionAutomorphism r where
 173  toFun := id
 174  preserves_event := fun _ => rfl
 175  invFun := id
 176  left_inv := fun _ => rfl
 177  right_inv := fun _ => rfl
 178