| Copyright | (c) The University of Glasgow 2001 |
|---|---|
| License | BSD-style (see the file libraries/base/LICENSE) |
| Maintainer | libraries@haskell.org |
| Stability | experimental |
| Portability | non-portable (MPTCs, uses Control.Monad.ST) |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
Data.Array.Base
Description
Basis for IArray and MArray. Not intended for external consumption; use IArray or MArray instead.
WARNING
This module is considered internal.
The Package Versioning Policy does not apply.
The contents of this module may change in any way whatsoever and without any warning between minor versions of this package.
Authors importing this module are expected to track development closely.
Synopsis
- class IArray a e where
- bounds :: Ix i => a i e -> (i, i)
- numElements :: Ix i => a i e -> Int
- unsafeArray :: Ix i => (i, i) -> [(Int, e)] -> a i e
- unsafeAt :: Ix i => a i e -> Int -> e
- unsafeReplace :: Ix i => a i e -> [(Int, e)] -> a i e
- unsafeAccum :: Ix i => (e -> e' -> e) -> a i e -> [(Int, e')] -> a i e
- unsafeAccumArray :: Ix i => (e -> e' -> e) -> e -> (i, i) -> [(Int, e')] -> a i e
- safeRangeSize :: Ix i => (i, i) -> Int
- safeIndex :: Ix i => (i, i) -> Int -> i -> Int
- unsafeReplaceST :: (IArray a e, Ix i) => a i e -> [(Int, e)] -> ST s (STArray s i e)
- unsafeAccumST :: (IArray a e, Ix i) => (e -> e' -> e) -> a i e -> [(Int, e')] -> ST s (STArray s i e)
- unsafeAccumArrayST :: Ix i => (e -> e' -> e) -> e -> (i, i) -> [(Int, e')] -> ST s (STArray s i e)
- array :: (IArray a e, Ix i) => (i, i) -> [(i, e)] -> a i e
- listArray :: (IArray a e, Ix i) => (i, i) -> [e] -> a i e
- genArray :: (IArray a e, Ix i) => (i, i) -> (i -> e) -> a i e
- listArrayST :: Ix i => (i, i) -> [e] -> ST s (STArray s i e)
- listUArrayST :: (MArray (STUArray s) e (ST s), Ix i) => (i, i) -> [e] -> ST s (STUArray s i e)
- type ListUArray e = forall i. Ix i => (i, i) -> [e] -> UArray i e
- (!) :: (IArray a e, Ix i) => a i e -> i -> e
- (!?) :: (IArray a e, Ix i) => a i e -> i -> Maybe e
- indices :: (IArray a e, Ix i) => a i e -> [i]
- elems :: (IArray a e, Ix i) => a i e -> [e]
- assocs :: (IArray a e, Ix i) => a i e -> [(i, e)]
- accumArray :: (IArray a e, Ix i) => (e -> e' -> e) -> e -> (i, i) -> [(i, e')] -> a i e
- (//) :: (IArray a e, Ix i) => a i e -> [(i, e)] -> a i e
- accum :: (IArray a e, Ix i) => (e -> e' -> e) -> a i e -> [(i, e')] -> a i e
- amap :: (IArray a e', IArray a e, Ix i) => (e' -> e) -> a i e' -> a i e
- ixmap :: (IArray a e, Ix i, Ix j) => (i, i) -> (i -> j) -> a j e -> a i e
- foldrArray :: (IArray a e, Ix i) => (e -> b -> b) -> b -> a i e -> b
- foldlArray' :: (IArray a e, Ix i) => (b -> e -> b) -> b -> a i e -> b
- foldlArray :: (IArray a e, Ix i) => (b -> e -> b) -> b -> a i e -> b
- foldrArray' :: (IArray a e, Ix i) => (e -> b -> b) -> b -> a i e -> b
- traverseArray_ :: (IArray a e, Ix i, Applicative f) => (e -> f b) -> a i e -> f ()
- forArray_ :: (IArray a e, Ix i, Applicative f) => a i e -> (e -> f b) -> f ()
- foldlArrayM' :: (IArray a e, Ix i, Monad m) => (b -> e -> m b) -> b -> a i e -> m b
- foldrArrayM' :: (IArray a e, Ix i, Monad m) => (e -> b -> m b) -> b -> a i e -> m b
- data UArray i e = UArray !i !i !Int ByteArray#
- unsafeArrayUArray :: (MArray (STUArray s) e (ST s), Ix i) => (i, i) -> [(Int, e)] -> e -> ST s (UArray i e)
- unsafeFreezeSTUArray :: STUArray s i e -> ST s (UArray i e)
- unsafeReplaceUArray :: (MArray (STUArray s) e (ST s), Ix i) => UArray i e -> [(Int, e)] -> ST s (UArray i e)
- unsafeAccumUArray :: (MArray (STUArray s) e (ST s), Ix i) => (e -> e' -> e) -> UArray i e -> [(Int, e')] -> ST s (UArray i e)
- unsafeAccumArrayUArray :: (MArray (STUArray s) e (ST s), Ix i) => (e -> e' -> e) -> e -> (i, i) -> [(Int, e')] -> ST s (UArray i e)
- eqUArray :: (IArray UArray e, Ix i, Eq e) => UArray i e -> UArray i e -> Bool
- cmpUArray :: (IArray UArray e, Ix i, Ord e) => UArray i e -> UArray i e -> Ordering
- cmpIntUArray :: (IArray UArray e, Ord e) => UArray Int e -> UArray Int e -> Ordering
- showsIArray :: (IArray a e, Ix i, Show i, Show e) => Int -> a i e -> ShowS
- readIArray :: (IArray a e, Ix i, Read i, Read e) => ReadPrec (a i e)
- nullStablePtr :: StablePtr a
- arrEleBottom :: a
- class Monad m => MArray a e m where
- getBounds :: Ix i => a i e -> m (i, i)
- getNumElements :: Ix i => a i e -> m Int
- newArray :: Ix i => (i, i) -> e -> m (a i e)
- newArray_ :: Ix i => (i, i) -> m (a i e)
- unsafeNewArray_ :: Ix i => (i, i) -> m (a i e)
- unsafeRead :: Ix i => a i e -> Int -> m e
- unsafeWrite :: Ix i => a i e -> Int -> e -> m ()
- newListArray :: (MArray a e m, Ix i) => (i, i) -> [e] -> m (a i e)
- newGenArray :: (MArray a e m, Ix i) => (i, i) -> (i -> m e) -> m (a i e)
- readArray :: (MArray a e m, Ix i) => a i e -> i -> m e
- writeArray :: (MArray a e m, Ix i) => a i e -> i -> e -> m ()
- modifyArray :: (MArray a e m, Ix i) => a i e -> i -> (e -> e) -> m ()
- modifyArray' :: (MArray a e m, Ix i) => a i e -> i -> (e -> e) -> m ()
- getElems :: (MArray a e m, Ix i) => a i e -> m [e]
- getAssocs :: (MArray a e m, Ix i) => a i e -> m [(i, e)]
- mapArray :: (MArray a e' m, MArray a e m, Ix i) => (e' -> e) -> a i e' -> m (a i e)
- mapIndices :: (MArray a e m, Ix i, Ix j) => (i, i) -> (i -> j) -> a j e -> m (a i e)
- foldlMArray' :: (MArray a e m, Ix i) => (b -> e -> b) -> b -> a i e -> m b
- foldrMArray' :: (MArray a e m, Ix i) => (e -> b -> b) -> b -> a i e -> m b
- foldlMArrayM' :: (MArray a e m, Ix i) => (b -> e -> m b) -> b -> a i e -> m b
- foldrMArrayM' :: (MArray a e m, Ix i) => (e -> b -> m b) -> b -> a i e -> m b
- mapMArrayM_ :: (MArray a e m, Ix i) => (e -> m b) -> a i e -> m ()
- forMArrayM_ :: (MArray a e m, Ix i) => a i e -> (e -> m b) -> m ()
- data STUArray s i e = STUArray !i !i !Int (MutableByteArray# s)
- unsafeNewArraySTUArray_ :: Ix i => (i, i) -> (Int# -> Int#) -> ST s (STUArray s i e)
- bOOL_SCALE :: Int# -> Int#
- wORD_SCALE :: Int# -> Int#
- dOUBLE_SCALE :: Int# -> Int#
- fLOAT_SCALE :: Int# -> Int#
- safe_scale :: Int# -> Int# -> Int#
- bOOL_INDEX :: Int# -> Int#
- bOOL_BIT :: Int# -> Word#
- bOOL_NOT_BIT :: Int# -> Word#
- freeze :: (Ix i, MArray a e m, IArray b e) => a i e -> m (b i e)
- freezeSTUArray :: STUArray s i e -> ST s (UArray i e)
- memcpy_freeze :: MutableByteArray# s -> MutableByteArray# s -> CSize -> IO (Ptr a)
- unsafeFreeze :: (Ix i, MArray a e m, IArray b e) => a i e -> m (b i e)
- thaw :: (Ix i, IArray a e, MArray b e m) => a i e -> m (b i e)
- thawSTUArray :: UArray i e -> ST s (STUArray s i e)
- memcpy_thaw :: MutableByteArray# s -> ByteArray# -> CSize -> IO (Ptr a)
- unsafeThaw :: (Ix i, IArray a e, MArray b e m) => a i e -> m (b i e)
- unsafeThawSTUArray :: UArray i e -> ST s (STUArray s i e)
- unsafeThawIOArray :: Array ix e -> IO (IOArray ix e)
- thawIOArray :: Array ix e -> IO (IOArray ix e)
- freezeIOArray :: IOArray ix e -> IO (Array ix e)
- unsafeFreezeIOArray :: IOArray ix e -> IO (Array ix e)
- castSTUArray :: STUArray s ix a -> ST s (STUArray s ix b)
Documentation
class IArray a e where Source #
Class of immutable array types.
An array type has the form (a i e) where a is the array type
constructor (kind * -> * -> *), i is the index type (a member of
the class Ix), and e is the element type. The IArray class is
parameterised over both a and e, so that instances specialised to
certain element types can be defined.
Minimal complete definition
Methods
bounds :: Ix i => a i e -> (i, i) Source #
Extracts the bounds of an immutable array
numElements :: Ix i => a i e -> Int Source #
unsafeArray :: Ix i => (i, i) -> [(Int, e)] -> a i e Source #
unsafeAt :: Ix i => a i e -> Int -> e Source #
unsafeReplace :: Ix i => a i e -> [(Int, e)] -> a i e Source #
unsafeAccum :: Ix i => (e -> e' -> e) -> a i e -> [(Int, e')] -> a i e Source #
unsafeAccumArray :: Ix i => (e -> e' -> e) -> e -> (i, i) -> [(Int, e')] -> a i e Source #
Instances
safeRangeSize :: Ix i => (i, i) -> Int Source #
unsafeAccumST :: (IArray a e, Ix i) => (e -> e' -> e) -> a i e -> [(Int, e')] -> ST s (STArray s i e) Source #
unsafeAccumArrayST :: Ix i => (e -> e' -> e) -> e -> (i, i) -> [(Int, e')] -> ST s (STArray s i e) Source #
Arguments
| :: (IArray a e, Ix i) | |
| => (i, i) | bounds of the array: (lowest,highest) |
| -> [(i, e)] | list of associations |
| -> a i e |
Constructs an immutable array from a pair of bounds and a list of initial associations.
The bounds are specified as a pair of the lowest and highest bounds in the array respectively. For example, a one-origin vector of length 10 has bounds (1,10), and a one-origin 10 by 10 matrix has bounds ((1,1),(10,10)).
An association is a pair of the form (i,x), which defines the value of
the array at index i to be x. The array is undefined if any index
in the list is out of bounds. If any two associations in the list have
the same index, the value at that index is implementation-dependent.
(In GHC, the last value specified for that index is used.
Other implementations will also do this for unboxed arrays, but Haskell
98 requires that for Array the value at such indices is bottom.)
Because the indices must be checked for these errors, array is
strict in the bounds argument and in the indices of the association
list. Whether array is strict or non-strict in the elements depends
on the array type: Array is a non-strict array type, but
all of the UArray arrays are strict. Thus in a
non-strict array, recurrences such as the following are possible:
a = array (1,100) ((1,1) : [(i, i * a!(i-1)) | i \<- [2..100]])
Not every index within the bounds of the array need appear in the association list, but the values associated with indices that do not appear will be undefined.
If, in any dimension, the lower bound is greater than the upper bound,
then the array is legal, but empty. Indexing an empty array always
gives an array-bounds error, but bounds still yields the bounds with
which the array was constructed.
listArray :: (IArray a e, Ix i) => (i, i) -> [e] -> a i e Source #
Constructs an immutable array from a list of initial elements. The list gives the elements of the array in ascending order beginning with the lowest index.
genArray :: (IArray a e, Ix i) => (i, i) -> (i -> e) -> a i e Source #
Constructs an immutable array using a generator function.
Since: 0.5.6.0
listUArrayST :: (MArray (STUArray s) e (ST s), Ix i) => (i, i) -> [e] -> ST s (STUArray s i e) Source #
type ListUArray e = forall i. Ix i => (i, i) -> [e] -> UArray i e Source #
(!) :: (IArray a e, Ix i) => a i e -> i -> e Source #
Returns the element of an immutable array at the specified index, or throws an exception if the index is out of bounds.
indices :: (IArray a e, Ix i) => a i e -> [i] Source #
Returns a list of all the valid indices in an array.
elems :: (IArray a e, Ix i) => a i e -> [e] Source #
Returns a list of all the elements of an array, in the same order as their indices.
assocs :: (IArray a e, Ix i) => a i e -> [(i, e)] Source #
Returns the contents of an array as a list of associations.
Arguments
| :: (IArray a e, Ix i) | |
| => (e -> e' -> e) | An accumulating function |
| -> e | A default element |
| -> (i, i) | The bounds of the array |
| -> [(i, e')] | List of associations |
| -> a i e | Returns: the array |
Constructs an immutable array from a list of associations. Unlike
array, the same index is allowed to occur multiple times in the list
of associations; an accumulating function is used to combine the
values of elements 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:
hist :: (Ix a, Num b) => (a,a) -> [a] -> Array a b hist bnds is = accumArray (+) 0 bnds [(i, 1) | i\<-is, inRange bnds i]
(//) :: (IArray a e, Ix i) => a i e -> [(i, e)] -> a i e Source #
Takes an array and a list of pairs and returns an array identical to
the left 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 m//[((i,i), 0) | i <- [1..n]] is the same matrix, except with
the diagonal zeroed.
As with the array function, if any two associations in the list have
the same index, the value at that index is implementation-dependent.
(In GHC, the last value specified for that index is used.
Other implementations will also do this for unboxed arrays, but Haskell
98 requires that for Array the value at such indices is bottom.)
For most array types, this operation is O(n) where n is the size of the array. However, the diffarray package provides an array type for which this operation has complexity linear in the number of updates.
accum :: (IArray a e, Ix i) => (e -> e' -> e) -> a i e -> [(i, e')] -> a i e Source #
accum f takes an array and an association list and accumulates pairs
from the list into the array with the accumulating function f. Thus
accumArray can be defined using accum:
accumArray f z b = accum f (array b [(i, z) | i \<- range b])
amap :: (IArray a e', IArray a e, Ix i) => (e' -> e) -> a i e' -> a i e Source #
Returns a new array derived from the original array by applying a function to each of the elements.
ixmap :: (IArray a e, Ix i, Ix j) => (i, i) -> (i -> j) -> a j e -> a i e Source #
Returns a new array derived from the original array by applying a function to each of the indices.
foldrArray :: (IArray a e, Ix i) => (e -> b -> b) -> b -> a i e -> b Source #
Lazy right-associative fold.
Since: 0.5.8.0
foldlArray' :: (IArray a e, Ix i) => (b -> e -> b) -> b -> a i e -> b Source #
Strict accumulating left-associative fold.
Since: 0.5.8.0
foldlArray :: (IArray a e, Ix i) => (b -> e -> b) -> b -> a i e -> b Source #
Lazy left-associative fold.
Since: 0.5.8.0
foldrArray' :: (IArray a e, Ix i) => (e -> b -> b) -> b -> a i e -> b Source #
Strict accumulating right-associative fold.
Since: 0.5.8.0
traverseArray_ :: (IArray a e, Ix i, Applicative f) => (e -> f b) -> a i e -> f () Source #
Map elements to applicative actions, sequence them left-to-right, and discard the results.
Since: 0.5.8.0
forArray_ :: (IArray a e, Ix i, Applicative f) => a i e -> (e -> f b) -> f () Source #
forArray_ is traverseArray_ with its arguments flipped.
Since: 0.5.8.0
foldlArrayM' :: (IArray a e, Ix i, Monad m) => (b -> e -> m b) -> b -> a i e -> m b Source #
Strict accumulating left-associative monadic fold.
Since: 0.5.8.0
foldrArrayM' :: (IArray a e, Ix i, Monad m) => (e -> b -> m b) -> b -> a i e -> m b Source #
Strict accumulating right-associative monadic fold.
Since: 0.5.8.0
Arrays with unboxed elements. Instances of IArray are provided
for UArray with certain element types (Int, Float, Char,
etc.; see the UArray class for a full list).
A UArray will generally be more efficient (in terms of both time
and space) than the equivalent Array with the same
element type. However, UArray is strict in its elements - so
don't use UArray if you require the non-strictness that
Array provides.
Because the IArray interface provides operations overloaded on
the type of the array, it should be possible to just change the
array type being used by a program from say Array to UArray to
get the benefits of unboxed arrays (don't forget to import
Data.Array.Unboxed instead of Data.Array).
Constructors
| UArray !i !i !Int ByteArray# |
Instances
unsafeArrayUArray :: (MArray (STUArray s) e (ST s), Ix i) => (i, i) -> [(Int, e)] -> e -> ST s (UArray i e) Source #
unsafeReplaceUArray :: (MArray (STUArray s) e (ST s), Ix i) => UArray i e -> [(Int, e)] -> ST s (UArray i e) Source #
unsafeAccumUArray :: (MArray (STUArray s) e (ST s), Ix i) => (e -> e' -> e) -> UArray i e -> [(Int, e')] -> ST s (UArray i e) Source #
unsafeAccumArrayUArray :: (MArray (STUArray s) e (ST s), Ix i) => (e -> e' -> e) -> e -> (i, i) -> [(Int, e')] -> ST s (UArray i e) Source #
nullStablePtr :: StablePtr a Source #
arrEleBottom :: a Source #
class Monad m => MArray a e m where Source #
Class of mutable array types.
An array type has the form (a i e) where a is the array type
constructor (kind * -> * -> *), i is the index type (a member of
the class Ix), and e is the element type.
The MArray class is parameterised over both a and e (so that
instances specialised to certain element types can be defined, in the
same way as for IArray), and also over the type of the monad, m,
in which the mutable array will be manipulated.
Minimal complete definition
getBounds, getNumElements, (newArray | unsafeNewArray_), unsafeRead, unsafeWrite
Methods
getBounds :: Ix i => a i e -> m (i, i) Source #
Returns the bounds of the array (lowest,highest).
getNumElements :: Ix i => a i e -> m Int Source #
Returns the number of elements in the array.
newArray :: Ix i => (i, i) -> e -> m (a i e) Source #
Builds a new array, with every element initialised to the supplied value. The first and second element of the tuple specifies the lowest and highest index, respectively.
newArray_ :: Ix i => (i, i) -> m (a i e) Source #
Builds a new array, with every element initialised to an undefined value. In a monadic context in which operations must be deterministic (e.g. the ST monad), the array elements are initialised to a fixed but undefined value, such as zero. The first and second element of the tuple specifies the lowest and highest index, respectively.
unsafeNewArray_ :: Ix i => (i, i) -> m (a i e) Source #
Builds a new array, with every element initialised to an undefined value. The first and second element of the tuple specifies the lowest and highest index, respectively.
unsafeRead :: Ix i => a i e -> Int -> m e Source #
unsafeWrite :: Ix i => a i e -> Int -> e -> m () Source #
Instances
newListArray :: (MArray a e m, Ix i) => (i, i) -> [e] -> m (a i e) Source #
Constructs a mutable array from a list of initial elements. The list gives the elements of the array in ascending order beginning with the lowest index. The first and second element of the tuple specifies the lowest and highest index, respectively.
newGenArray :: (MArray a e m, Ix i) => (i, i) -> (i -> m e) -> m (a i e) Source #
Constructs a mutable array using a generator function. It invokes the generator function in ascending order of the indices.
Since: 0.5.6.0
writeArray :: (MArray a e m, Ix i) => a i e -> i -> e -> m () Source #
Write an element in a mutable array
modifyArray :: (MArray a e m, Ix i) => a i e -> i -> (e -> e) -> m () Source #
Modify an element in a mutable array
Since: 0.5.6.0
modifyArray' :: (MArray a e m, Ix i) => a i e -> i -> (e -> e) -> m () Source #
Modify an element in a mutable array. Strict in the written element.
Since: 0.5.6.0
getElems :: (MArray a e m, Ix i) => a i e -> m [e] Source #
Return a list of all the elements of a mutable array
getAssocs :: (MArray a e m, Ix i) => a i e -> m [(i, e)] Source #
Return a list of all the associations of a mutable array, in index order.
mapArray :: (MArray a e' m, MArray a e m, Ix i) => (e' -> e) -> a i e' -> m (a i e) Source #
Constructs a new array derived from the original array by applying a function to each of the elements.
mapIndices :: (MArray a e m, Ix i, Ix j) => (i, i) -> (i -> j) -> a j e -> m (a i e) Source #
Constructs a new array derived from the original array by applying a function to each of the indices.
foldlMArray' :: (MArray a e m, Ix i) => (b -> e -> b) -> b -> a i e -> m b Source #
Strict accumulating left-associative fold.
Since: 0.5.8.0
foldrMArray' :: (MArray a e m, Ix i) => (e -> b -> b) -> b -> a i e -> m b Source #
Strict accumulating right-associative fold.
Since: 0.5.8.0
foldlMArrayM' :: (MArray a e m, Ix i) => (b -> e -> m b) -> b -> a i e -> m b Source #
Strict accumulating left-associative monadic fold.
Since: 0.5.8.0
foldrMArrayM' :: (MArray a e m, Ix i) => (e -> b -> m b) -> b -> a i e -> m b Source #
Strict accumulating right-associative monadic fold.
Since: 0.5.8.0
mapMArrayM_ :: (MArray a e m, Ix i) => (e -> m b) -> a i e -> m () Source #
Map elements to monadic actions, sequence them left-to-right, and discard the results.
Since: 0.5.8.0
forMArrayM_ :: (MArray a e m, Ix i) => a i e -> (e -> m b) -> m () Source #
forMArrayM_ is mapMArrayM_ with its arguments flipped.
Since: 0.5.8.0
A mutable array with unboxed elements, that can be manipulated in
the ST monad. The type arguments are as follows:
s: the state variable argument for theSTtypei: the index type of the array (should be an instance ofIx)e: the element type of the array. Only certain element types are supported.
An STUArray will generally be more efficient (in terms of both time
and space) than the equivalent boxed version (STArray) with the same
element type. However, STUArray is strict in its elements - so
don't use STUArray if you require the non-strictness that
STArray provides.
Constructors
| STUArray !i !i !Int (MutableByteArray# s) |
Instances
bOOL_SCALE :: Int# -> Int# Source #
wORD_SCALE :: Int# -> Int# Source #
dOUBLE_SCALE :: Int# -> Int# Source #
fLOAT_SCALE :: Int# -> Int# Source #
bOOL_INDEX :: Int# -> Int# Source #
The index of the word which the given Bool array elements falls within.
bOOL_NOT_BIT :: Int# -> Word# Source #
memcpy_freeze :: MutableByteArray# s -> MutableByteArray# s -> CSize -> IO (Ptr a) Source #
unsafeFreeze :: (Ix i, MArray a e m, IArray b e) => a i e -> m (b i e) Source #
Converts an mutable array into an immutable array. The implementation may either simply cast the array from one type to the other without copying the array, or it may take a full copy of the array.
Note that because the array is possibly not copied, any subsequent modifications made to the mutable version of the array may be shared with the immutable version. It is safe to use, therefore, if the mutable version is never modified after the freeze operation.
The non-copying implementation is supported between certain pairs
of array types only; one constraint is that the array types must
have identical representations. In GHC, The following pairs of
array types have a non-copying O(1) implementation of
unsafeFreeze. Because the optimised versions are enabled by
specialisations, you will need to compile with optimisation (-O) to
get them.
memcpy_thaw :: MutableByteArray# s -> ByteArray# -> CSize -> IO (Ptr a) Source #
unsafeThaw :: (Ix i, IArray a e, MArray b e m) => a i e -> m (b i e) Source #
Converts an immutable array into a mutable array. The implementation may either simply cast the array from one type to the other without copying the array, or it may take a full copy of the array.
Note that because the array is possibly not copied, any subsequent modifications made to the mutable version of the array may be shared with the immutable version. It is only safe to use, therefore, if the immutable array is never referenced again in this thread, and there is no possibility that it can be also referenced in another thread. If you use an unsafeThawwriteunsafeFreeze sequence in a multi-threaded setting, then you must ensure that this sequence is atomic with respect to other threads, or a garbage collector crash may result (because the write may be writing to a frozen array).
The non-copying implementation is supported between certain pairs
of array types only; one constraint is that the array types must
have identical representations. In GHC, The following pairs of
array types have a non-copying O(1) implementation of
unsafeThaw. Because the optimised versions are enabled by
specialisations, you will need to compile with optimisation (-O) to
get them.