52 lines
2 KiB
Text
52 lines
2 KiB
Text
/-
|
|
Copyright (c) 2016 Microsoft Corporation. All rights reserved.
|
|
Released under Apache 2.0 license as described in the file LICENSE.
|
|
Author: Leonardo de Moura
|
|
-/
|
|
definition map (A B : Type) := A → option B
|
|
|
|
namespace map
|
|
variables {A B : Type}
|
|
open tactic
|
|
|
|
definition empty : map A B :=
|
|
λ a, none
|
|
|
|
definition lookup (k : A) (m : map A B) : option B :=
|
|
m k
|
|
|
|
theorem ext (m₁ m₂ : map A B) : (∀ a, lookup a m₁ = lookup a m₂) → m₁ = m₂ :=
|
|
funext
|
|
|
|
theorem lookup_empty (k : A) : lookup k (empty : map A B) = none :=
|
|
rfl
|
|
|
|
variable [decidable_eq A]
|
|
|
|
definition insert (k : A) (v : B) (m : map A B) : map A B :=
|
|
λ a, if a = k then some v else m a
|
|
|
|
theorem lookup_insert (k : A) (v : B) (m : map A B) : lookup k (insert k v m) = some v :=
|
|
by unfold [`map.insert, `map.lookup] >> dsimp >> rewrite `if_pos >> reflexivity
|
|
|
|
theorem lookup_insert_of_ne {k₁ k₂ : A} (v : B) (m : map A B) : k₁ ≠ k₂ → lookup k₁ (insert k₂ v m) = lookup k₁ m :=
|
|
by intros >> unfold [`map.insert, `map.lookup] >> dsimp >> rewrite `if_neg >> assumption
|
|
|
|
definition erase (k : A) (m : map A B) : map A B :=
|
|
λ a, if a = k then none else m a
|
|
|
|
theorem lookup_erase (k : A) (v : B) (m : map A B) : lookup k (erase k m) = none :=
|
|
by unfold [`map.erase, `map.lookup] >> dsimp >> rewrite `if_pos >> reflexivity
|
|
|
|
theorem lookup_erase_of_ne {k₁ k₂ : A} (v : B) (m : map A B) : k₁ ≠ k₂ → lookup k₁ (erase k₂ m) = lookup k₁ m :=
|
|
by intros >> unfold [`map.erase, `map.lookup] >> dsimp >> rewrite `if_neg >> assumption
|
|
|
|
theorem erase_empty (k : A) : erase k empty = (empty : map A B) :=
|
|
funext (λ a, by unfold [`map.erase, `map.empty] >> rewrite `if_t_t)
|
|
|
|
theorem erase_insert {k : A} {m : map A B} (v : B) : lookup k m = none → erase k (insert k v m) = m :=
|
|
assume h, funext (λ a, decidable.by_cases
|
|
(suppose a = k, by get_local `this >>= subst >> unfold [`map.erase, `map.insert] >> rewrite `if_pos >> symmetry >> assumption >> reflexivity)
|
|
(suppose a ≠ k, by unfold [`map.erase, `map.insert] >> rewrite `if_neg >> dsimp >> rewrite `if_neg >> repeat assumption))
|
|
|
|
end map
|