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Fix v2.1-rc1 by reverting (some) changes to Data.List.* #2423

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Merged
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Jul 5, 2024
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Fix v2.1-rc1 by reverting (some) changes to Data.List.* #2423

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46 changes: 20 additions & 26 deletions src/Data/List/Base.agda
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Original file line number Diff line number Diff line change
Expand Up @@ -358,49 +358,45 @@ removeAt (x ∷ xs) (suc i) = x ∷ removeAt xs i

takeWhile : ∀ {P : Pred A p} → Decidable P → List A → List A
takeWhile P? [] = []
takeWhile P? (x ∷ xs) = if does (P? x)
then x ∷ takeWhile P? xs
else []
takeWhile P? (x ∷ xs) with does (P? x)
... | true = x ∷ takeWhile P? xs
... | false = []

takeWhileᵇ : (A → Bool) → List A → List A
takeWhileᵇ p = takeWhile (T? ∘ p)

dropWhile : ∀ {P : Pred A p} → Decidable P → List A → List A
dropWhile P? [] = []
dropWhile P? (x ∷ xs) = if does (P? x)
then dropWhile P? xs
else x ∷ xs
dropWhile P? (x ∷ xs) with does (P? x)
... | true = dropWhile P? xs
... | false = x ∷ xs

dropWhileᵇ : (A → Bool) → List A → List A
dropWhileᵇ p = dropWhile (T? ∘ p)

filter : ∀ {P : Pred A p} → Decidable P → List A → List A
filter P? [] = []
filter P? (x ∷ xs) =
let xs′ = filter P? xs in
if does (P? x)
then x ∷ xs′
else xs′
filter P? (x ∷ xs) with does (P? x)
... | false = filter P? xs
... | true = x ∷ filter P? xs

filterᵇ : (A → Bool) → List A → List A
filterᵇ p = filter (T? ∘ p)

partition : ∀ {P : Pred A p} → Decidable P → List A → (List A × List A)
partition P? [] = [] , []
partition P? (x ∷ xs) =
let ys , zs = partition P? xs in
if does (P? x)
then (x ∷ ys , zs)
else (ys , x ∷ zs)
partition P? [] = ([] , [])
partition P? (x ∷ xs) with does (P? x) | partition P? xs
... | true | (ys , zs) = (x ∷ ys , zs)
... | false | (ys , zs) = (ys , x ∷ zs)

partitionᵇ : (A → Bool) → List A → List A × List A
partitionᵇ p = partition (T? ∘ p)

span : ∀ {P : Pred A p} → Decidable P → List A → (List A × List A)
span P? [] = [] , []
span P? ys@(x ∷ xs) = if does (P? x)
then Product.map (x ∷_) id (span P? xs)
else ([] , ys)
span P? [] = ([] , [])
span P? ys@(x ∷ xs) with does (P? x)
... | true = Product.map (x ∷_) id (span P? xs)
... | false = ([] , ys)


spanᵇ : (A → Bool) → List A → List A × List A
Expand Down Expand Up @@ -452,11 +448,9 @@ wordsByᵇ p = wordsBy (T? ∘ p)
derun : ∀ {R : Rel A p} → B.Decidable R → List A → List A
derun R? [] = []
derun R? (x ∷ []) = x ∷ []
derun R? (x ∷ xs@(y ∷ _)) =
let ys = derun R? xs in
if does (R? x y)
then ys
else x ∷ ys
derun R? (x ∷ xs@(y ∷ _)) with does (R? x y) | derun R? xs
... | true | ys = ys
... | false | ys = x ∷ ys

derunᵇ : (A → A → Bool) → List A → List A
derunᵇ r = derun (T? ∘₂ r)
Expand Down
30 changes: 15 additions & 15 deletions src/Data/List/Properties.agda
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Original file line number Diff line number Diff line change
Expand Up @@ -1163,13 +1163,13 @@ module _ {P : Pred A p} (P? : Decidable P) where
filter-all : ∀ {xs} → All P xs → filter P? xs ≡ xs
filter-all {[]} [] = refl
filter-all {x ∷ xs} (px ∷ pxs) with P? x
... | false because [¬px] = contradiction px (invert [¬px])
... | true because _ = cong (x ∷_) (filter-all pxs)
... | no ¬px = contradiction px ¬px
... | true because _ = cong (x ∷_) (filter-all pxs)

filter-notAll : ∀ xs → Any (∁ P) xs → length (filter P? xs) < length xs
filter-notAll (x ∷ xs) (here ¬px) with P? x
... | false because _ = s≤s (length-filter xs)
... | true because [px] = contradiction (invert [px]) ¬px
... | false because _ = s≤s (length-filter xs)
... | yes px = contradiction px ¬px
filter-notAll (x ∷ xs) (there any) with ih ← filter-notAll xs any | does (P? x)
... | false = m≤n⇒m≤1+n ih
... | true = s≤s ih
Expand All @@ -1185,8 +1185,8 @@ module _ {P : Pred A p} (P? : Decidable P) where
filter-none : ∀ {xs} → All (∁ P) xs → filter P? xs ≡ []
filter-none {[]} [] = refl
filter-none {x ∷ xs} (¬px ∷ ¬pxs) with P? x
... | false because _ = filter-none ¬pxs
... | true because [px] = contradiction (invert [px]) ¬px
... | false because _ = filter-none ¬pxs
... | yes px = contradiction px ¬px

filter-complete : ∀ {xs} → length (filter P? xs) ≡ length xs →
filter P? xs ≡ xs
Expand All @@ -1197,13 +1197,13 @@ module _ {P : Pred A p} (P? : Decidable P) where

filter-accept : ∀ {x xs} → P x → filter P? (x ∷ xs) ≡ x ∷ (filter P? xs)
filter-accept {x} Px with P? x
... | true because _ = refl
... | false because [¬Px] = contradiction Px (invert [¬Px])
... | true because _ = refl
... | no ¬Px = contradiction Px ¬Px

filter-reject : ∀ {x xs} → ¬ P x → filter P? (x ∷ xs) ≡ filter P? xs
filter-reject {x} ¬Px with P? x
... | true because [Px] = contradiction (invert [Px]) ¬Px
... | false because _ = refl
... | yes Px = contradiction Px ¬Px
... | false because _ = refl

filter-idem : filter P? ∘ filter P? ≗ filter P?
filter-idem [] = refl
Expand Down Expand Up @@ -1241,13 +1241,13 @@ module _ {R : Rel A p} (R? : B.Decidable R) where

derun-reject : ∀ {x y} xs → R x y → derun R? (x ∷ y ∷ xs) ≡ derun R? (y ∷ xs)
derun-reject {x} {y} xs Rxy with R? x y
... | true because _ = refl
... | false because [¬Rxy] = contradiction Rxy (invert [¬Rxy])
... | yes _ = refl
... | no ¬Rxy = contradiction Rxy ¬Rxy

derun-accept : ∀ {x y} xs → ¬ R x y → derun R? (x ∷ y ∷ xs) ≡ x ∷ derun R? (y ∷ xs)
derun-accept {x} {y} xs ¬Rxy with R? x y
... | true because [Rxy] = contradiction (invert [Rxy]) ¬Rxy
... | false because _ = refl
... | yes Rxy = contradiction Rxy ¬Rxy
... | no _ = refl

------------------------------------------------------------------------
-- partition
Expand All @@ -1260,7 +1260,7 @@ module _ {P : Pred A p} (P? : Decidable P) where
... | true = cong (Product.map (x ∷_) id) ih
... | false = cong (Product.map id (x ∷_)) ih

length-partition : ∀ xs → (let ys , zs = partition P? xs) →
length-partition : ∀ xs → (let (ys , zs) = partition P? xs) →
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Was this change necessary?

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@jamesmckinna jamesmckinna Jul 4, 2024 •
edited
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No, not sure how it crept in, or why!?

UPDATED: hang on! This PR reverts previous changes, so those things were likely part of the original Data.List.Properties definitions... and suggest a downstream v2.2 to fix these (and many other things around this anomaly) later...?

length ys ≤ length xs × length zs ≤ length xs
length-partition [] = z≤n , z≤n
length-partition (x ∷ xs) with ih ← length-partition xs | does (P? x)
Expand Down