Add fold functions for arrays
1 unresolved thread
1 unresolved thread
At the moment it is quite difficult to perform some folds on some arrays.
- In general, arrays can be folded over by folding over the range of indices and then indexing into the array. This is a little cumbersome, and also inefficient when folding right-to-left because Ix does not offer reversed range generation.
- Alternately, Array has a Foldable instance which works great, but UArray cannot be Foldable. Folds on UArray can instead be done via elems. Due to list fusion, this works out well for some folds (foldr, foldl'), but not others (foldr').
- For mutable arrays, there are no alternate ways to fold.
This commit adds some commonly used folds for arrays and mutable arrays to improve this situation.
Fixes #16 (closed).
Edited by meooow
Merge request reports
Activity
mentioned in issue #17 (closed)
1141 foldrMArrayM' :: (MArray a e m, Ix i) => (e -> b -> m b) -> b -> a i e -> m b 1142 foldrMArrayM' f z0 = \a -> do 1143 !n <- getNumElements a 1144 let go i !z | i < 0 = pure z 1145 | otherwise = do 1146 x <- unsafeRead a i 1147 z' <- f x z 1148 go (i-1) z' 1149 go (n-1) z0 1150 {-# INLINE foldrMArrayM' #-} 1151 1152 -- | Map elements to monadic actions, sequence them left-to-right, and discard 1153 -- the results. 1154 -- 1155 -- @since FIXME 1156 mapMArrayM_ :: (MArray a e m, Ix i) => (e -> m b) -> a i e -> m () added 3 commits
-
62285d38...47143aad - 2 commits from branch
ghc/packages:master - 9dd4cc32 - Add fold functions for arrays
-
62285d38...47143aad - 2 commits from branch
Please register or sign in to reply