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Merged
meooow25 merged 2 commits into from
Apr 3, 2026
Merged

Add Data.Sequence.toList #1192

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5599e68
Add Data.Sequence.toList
meooow25 Mar 29, 2026
3d86bec
Add doc suggestion
meooow25 Mar 29, 2026
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6 changes: 3 additions & 3 deletions containers-tests/tests/seq-properties.hs
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Expand Up @@ -22,7 +22,7 @@ import Control.Arrow ((***))
import Control.Monad.Trans.State.Strict
import Data.Array (listArray)
import Data.Coerce (coerce)
import Data.Foldable (Foldable(foldl, foldl1, foldr, foldr1, foldMap, fold), toList, all, sum, foldl', foldr')
import Data.Foldable (Foldable(foldl, foldl1, foldr, foldr1, foldMap, fold), all, sum, foldl', foldr')
import Data.Functor ((<$>), (<$))
import Data.Maybe (listToMaybe)
import qualified Data.Maybe as Maybe
Expand Down Expand Up @@ -194,8 +194,8 @@ instance (Arbitrary a, Sized a) => Arbitrary (FingerTree a) where
arb n = do
pr <- arbitrary
sf <- arbitrary
let n_pr = Prelude.length (toList pr)
let n_sf = Prelude.length (toList sf)
let n_pr = Prelude.length pr
n_sf = Prelude.length sf
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@treeowl treeowl Mar 29, 2026

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Whoa... Any idea why we had such a uselessly inefficient length calculation here before?

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@meooow25 meooow25 Mar 29, 2026

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These are Digits so it's up to 4 elements and I don't think it is noticeable. It might even end up the same after inlining and optimizations.

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@treeowl treeowl Mar 29, 2026

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Oh yeah, I got mixed up. Still better to get it right.

-- adding n `div` 7 ensures that n_m >= 0, and makes more Singles
let n_m = max (n `div` 7) ((n - n_pr - n_sf) `div` 3)
m <- arb n_m
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2 changes: 2 additions & 0 deletions containers/src/Data/Sequence.hs
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Expand Up @@ -172,6 +172,8 @@ module Data.Sequence (
viewl, -- :: Seq a -> ViewL a
ViewR(..),
viewr, -- :: Seq a -> ViewR a
-- ** List
toList,
-- * Scans
scanl, -- :: (a -> b -> a) -> a -> Seq b -> Seq a
scanl1, -- :: (a -> a -> a) -> Seq a -> Seq a
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16 changes: 13 additions & 3 deletions containers/src/Data/Sequence/Internal.hs
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Expand Up @@ -107,6 +107,8 @@ module Data.Sequence.Internal (
viewl, -- :: Seq a -> ViewL a
ViewR(..),
viewr, -- :: Seq a -> ViewR a
-- ** List
toList,
-- * Scans
scanl, -- :: (a -> b -> a) -> a -> Seq b -> Seq a
scanl1, -- :: (a -> a -> a) -> Seq a -> Seq a
Expand Down Expand Up @@ -197,7 +199,7 @@ import Control.Monad (MonadPlus(..))
import Data.Monoid (Monoid(..))
import Data.Functor (Functor(..))
import Utils.Containers.Internal.State (State(..), execState)
import Data.Foldable (foldr', toList)
import Data.Foldable (foldr')
import qualified Data.Foldable as F

import qualified Data.Semigroup as Semigroup
Expand Down Expand Up @@ -2375,6 +2377,12 @@ viewRTree (Deep s pr m (Three x y z)) =
viewRTree (Deep s pr m (Four w x y z)) =
SnocRTree (Deep (s - size z) pr m (Three w x y)) z

-- | \(O(n)\). Convert to a list of elements.
--
-- @since FIXME
toList :: Seq a -> [a]
toList = F.toList

------------------------------------------------------------------------
-- Scans
--
Expand Down Expand Up @@ -4316,8 +4324,10 @@ findIndicesR p xs = foldlWithIndex g [] xs
-- eventually find a less mind-bending way to accomplish this.

-- | \( O(n) \). Create a sequence from a finite list of elements.
-- There is a function 'toList' in the opposite direction for all
-- instances of the 'Foldable' class, including 'Seq'.
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--
-- @'fromList' . 'toList' = id@
--
-- For any finite list @xs@, @'toList' ('fromList' xs) = xs@.
fromList :: [a] -> Seq a
-- Note: we can avoid map_elem if we wish by scattering
-- Elem applications throughout mkTreeE and getNodesE, but
Expand Down
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