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chore: split Init.Data.Array.Lemmas for better bootstrapping (#5255)
This allows significantly reducing the imports of `Init.Data.List.Impl`.
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/- | ||
Copyright (c) 2022 Mario Carneiro. All rights reserved. | ||
Released under Apache 2.0 license as described in the file LICENSE. | ||
Authors: Mario Carneiro | ||
-/ | ||
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prelude | ||
import Init.Data.List.TakeDrop | ||
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/-! | ||
## Bootstrapping theorems about arrays | ||
This file contains some theorems about `Array` and `List` needed for `Init.Data.List.Impl`. | ||
-/ | ||
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namespace Array | ||
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theorem foldlM_eq_foldlM_data.aux [Monad m] | ||
(f : β → α → m β) (arr : Array α) (i j) (H : arr.size ≤ i + j) (b) : | ||
foldlM.loop f arr arr.size (Nat.le_refl _) i j b = (arr.data.drop j).foldlM f b := by | ||
unfold foldlM.loop | ||
split; split | ||
· cases Nat.not_le_of_gt ‹_› (Nat.zero_add _ ▸ H) | ||
· rename_i i; rw [Nat.succ_add] at H | ||
simp [foldlM_eq_foldlM_data.aux f arr i (j+1) H] | ||
rw (config := {occs := .pos [2]}) [← List.get_drop_eq_drop _ _ ‹_›] | ||
rfl | ||
· rw [List.drop_of_length_le (Nat.ge_of_not_lt ‹_›)]; rfl | ||
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theorem foldlM_eq_foldlM_data [Monad m] | ||
(f : β → α → m β) (init : β) (arr : Array α) : | ||
arr.foldlM f init = arr.data.foldlM f init := by | ||
simp [foldlM, foldlM_eq_foldlM_data.aux] | ||
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theorem foldl_eq_foldl_data (f : β → α → β) (init : β) (arr : Array α) : | ||
arr.foldl f init = arr.data.foldl f init := | ||
List.foldl_eq_foldlM .. ▸ foldlM_eq_foldlM_data .. | ||
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theorem foldrM_eq_reverse_foldlM_data.aux [Monad m] | ||
(f : α → β → m β) (arr : Array α) (init : β) (i h) : | ||
(arr.data.take i).reverse.foldlM (fun x y => f y x) init = foldrM.fold f arr 0 i h init := by | ||
unfold foldrM.fold | ||
match i with | ||
| 0 => simp [List.foldlM, List.take] | ||
| i+1 => rw [← List.take_concat_get _ _ h]; simp [← (aux f arr · i)]; rfl | ||
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theorem foldrM_eq_reverse_foldlM_data [Monad m] (f : α → β → m β) (init : β) (arr : Array α) : | ||
arr.foldrM f init = arr.data.reverse.foldlM (fun x y => f y x) init := by | ||
have : arr = #[] ∨ 0 < arr.size := | ||
match arr with | ⟨[]⟩ => .inl rfl | ⟨a::l⟩ => .inr (Nat.zero_lt_succ _) | ||
match arr, this with | _, .inl rfl => rfl | arr, .inr h => ?_ | ||
simp [foldrM, h, ← foldrM_eq_reverse_foldlM_data.aux, List.take_length] | ||
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theorem foldrM_eq_foldrM_data [Monad m] | ||
(f : α → β → m β) (init : β) (arr : Array α) : | ||
arr.foldrM f init = arr.data.foldrM f init := by | ||
rw [foldrM_eq_reverse_foldlM_data, List.foldlM_reverse] | ||
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theorem foldr_eq_foldr_data (f : α → β → β) (init : β) (arr : Array α) : | ||
arr.foldr f init = arr.data.foldr f init := | ||
List.foldr_eq_foldrM .. ▸ foldrM_eq_foldrM_data .. | ||
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@[simp] theorem push_data (arr : Array α) (a : α) : (arr.push a).data = arr.data ++ [a] := by | ||
simp [push, List.concat_eq_append] | ||
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@[simp] theorem toListAppend_eq (arr : Array α) (l) : arr.toListAppend l = arr.data ++ l := by | ||
simp [toListAppend, foldr_eq_foldr_data] | ||
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@[simp] theorem toList_eq (arr : Array α) : arr.toList = arr.data := by | ||
simp [toList, foldr_eq_foldr_data] | ||
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@[simp] theorem pop_data (arr : Array α) : arr.pop.data = arr.data.dropLast := rfl | ||
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@[simp] theorem append_eq_append (arr arr' : Array α) : arr.append arr' = arr ++ arr' := rfl | ||
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@[simp] theorem append_data (arr arr' : Array α) : | ||
(arr ++ arr').data = arr.data ++ arr'.data := by | ||
rw [← append_eq_append]; unfold Array.append | ||
rw [foldl_eq_foldl_data] | ||
induction arr'.data generalizing arr <;> simp [*] | ||
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@[simp] theorem appendList_eq_append | ||
(arr : Array α) (l : List α) : arr.appendList l = arr ++ l := rfl | ||
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@[simp] theorem appendList_data (arr : Array α) (l : List α) : | ||
(arr ++ l).data = arr.data ++ l := by | ||
rw [← appendList_eq_append]; unfold Array.appendList | ||
induction l generalizing arr <;> simp [*] | ||
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end Array |
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