diff options
Diffstat (limited to 'libraries')
| -rw-r--r-- | libraries/base/GHC/Arr.hs | 30 |
1 files changed, 23 insertions, 7 deletions
diff --git a/libraries/base/GHC/Arr.hs b/libraries/base/GHC/Arr.hs index adfd602d9d..3698852076 100644 --- a/libraries/base/GHC/Arr.hs +++ b/libraries/base/GHC/Arr.hs @@ -1,5 +1,6 @@ {-# LANGUAGE Unsafe #-} {-# LANGUAGE NoImplicitPrelude, MagicHash, UnboxedTuples, RoleAnnotations #-} +{-# LANGUAGE BangPatterns #-} {-# OPTIONS_HADDOCK hide #-} ----------------------------------------------------------------------------- @@ -505,7 +506,7 @@ listArray (l,u) es = runST (ST $ \s1# -> -- | The value at the given index in an array. {-# INLINE (!) #-} (!) :: Ix i => Array i e -> i -> e -arr@(Array l u n _) ! i = unsafeAt arr $ safeIndex (l,u) n i +(!) arr@(Array l u n _) i = unsafeAt arr $ safeIndex (l,u) n i {-# INLINE safeRangeSize #-} safeRangeSize :: Ix i => (i, i) -> Int @@ -636,6 +637,7 @@ assocs arr@(Array l u _ _) = -- | The 'accumArray' function deals with repeated indices in the association -- list using an /accumulating function/ which combines the values of -- associations with the same index. +-- -- For example, given a list of values of some index type, @hist@ -- produces a histogram of the number of occurrences of each index within -- a specified range: @@ -643,10 +645,10 @@ assocs arr@(Array l u _ _) = -- > hist :: (Ix a, Num b) => (a,a) -> [a] -> Array a b -- > hist bnds is = accumArray (+) 0 bnds [(i, 1) | i<-is, inRange bnds i] -- --- If the accumulating function is strict, then 'accumArray' is strict in --- the values, as well as the indices, in the association list. Thus, --- unlike ordinary arrays built with 'array', accumulated arrays should --- not in general be recursive. +-- @accumArray@ is strict in each result of applying the accumulating +-- function, although it is lazy in the initial value. Thus, unlike +-- arrays built with 'array', accumulated arrays should not in general +-- be recursive. {-# INLINE accumArray #-} accumArray :: Ix i => (e -> a -> e) -- ^ accumulating function @@ -667,7 +669,7 @@ unsafeAccumArray f initial b ies = unsafeAccumArray' f initial b (rangeSize b) i unsafeAccumArray' :: (e -> a -> e) -> e -> (i,i) -> Int -> [(Int, a)] -> Array i e unsafeAccumArray' f initial (l,u) n@(I# n#) ies = runST (ST $ \s1# -> case newArray# n# initial s1# of { (# s2#, marr# #) -> - foldr (adjust f marr#) (done l u n marr#) ies s2# }) + foldr (adjust' f marr#) (done l u n marr#) ies s2# }) {-# INLINE adjust #-} adjust :: (e -> a -> e) -> MutableArray# s e -> (Int, a) -> STRep s b -> STRep s b @@ -678,6 +680,18 @@ adjust f marr# (I# i#, new) next case writeArray# marr# i# (f old new) s2# of s3# -> next s3# +{-# INLINE adjust' #-} +adjust' :: (e -> a -> e) + -> MutableArray# s e + -> (Int, a) + -> STRep s b -> STRep s b +adjust' f marr# (I# i#, new) next + = \s1# -> case readArray# marr# i# s1# of + (# s2#, old #) -> + let !combined = f old new + in next (writeArray# marr# i# combined s2#) + + -- | Constructs an array identical to the first argument except that it has -- been updated by the associations in the right argument. -- For example, if @m@ is a 1-origin, @n@ by @n@ matrix, then @@ -706,6 +720,8 @@ unsafeReplace arr ies = runST (do -- -- > accumArray f z b = accum f (array b [(i, z) | i <- range b]) -- +-- @accum@ is strict in all the results of applying the accumulation. +-- However, it is lazy in the initial values of the array. {-# INLINE accum #-} accum :: Ix i => (e -> a -> e) -> Array i e -> [(i, a)] -> Array i e accum f arr@(Array l u n _) ies = @@ -715,7 +731,7 @@ accum f arr@(Array l u n _) ies = unsafeAccum :: (e -> a -> e) -> Array i e -> [(Int, a)] -> Array i e unsafeAccum f arr ies = runST (do STArray l u n marr# <- thawSTArray arr - ST (foldr (adjust f marr#) (done l u n marr#) ies)) + ST (foldr (adjust' f marr#) (done l u n marr#) ies)) {-# INLINE [1] amap #-} -- See Note [amap] amap :: (a -> b) -> Array i a -> Array i b |