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feat(library/init/data/array/basic): add iterate₂ and foldl₂

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Leonardo de Moura 2019-04-29 10:12:01 -07:00
parent 5298841def
commit 63442ebde7
1 changed files with 23 additions and 0 deletions
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23
library/init/data/array/basic.lean
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@ -133,6 +133,23 @@ miterate a b (λ _, f)
@[inline] def mfoldlFrom (a : Array α) (b : β) (f : α → β → m β) (ini : Nat := 0) : m β :=
miterateAux a (λ _, f) ini b
-- TODO(Leo): justify termination using wf-rec
@[specialize] partial def miterate₂Aux (a₁ a₂ : Array α) (f : Π i : Fin a₁.size, α → α → β → m β) : Nat → β → m β
| i b :=
if h₁ : i < a₁.size then
let idx₁ : Fin a₁.size := ⟨i, h₁⟩ in
if h₂ : i < a₂.size then
let idx₂ : Fin a₂.size := ⟨i, h₂⟩ in
f idx₁ (a₁.index idx₁) (a₂.index idx₂) b >>= miterate₂Aux (i+1)
else pure b
else pure b
@[inline] def miterate₂ (a₁ a₂ : Array α) (b : β) (f : Π i : Fin a₁.size, α → α → β → m β) : m β :=
miterate₂Aux a₁ a₂ f 0 b
@[inline] def mfoldl₂ (a₁ a₂ : Array α) (b : β) (f : α → α → β → m β) : m β :=
miterate₂ a₁ a₂ b (λ _, f)
local attribute [instance] monadInhabited
-- TODO(Leo): justify termination using wf-rec
@ -160,6 +177,12 @@ iterate a b (λ _, f)
@[inline] def foldlFrom (a : Array α) (f : α → β → β) (b : β) (ini : Nat := 0) : β :=
Id.run $ mfoldlFrom a b f ini
@[inline] def iterate₂ (a₁ a₂ : Array α) (b : β) (f : Π i : Fin a₁.size, α → α → β → β) : β :=
Id.run $ miterate₂Aux a₁ a₂ f 0 b
@[inline] def foldl₂ (a₁ a₂ : Array α) (f : α → α → β → β) (b : β) : β :=
iterate₂ a₁ a₂ b (λ _, f)
@[inline] def find (a : Array α) (f : α → Option β) : Option β :=
Id.run $ mfindAux a f 0