array-0.4.0.1: Mutable and immutable arrays

Portabilitynon-portable (uses Data.Array.Base)
Stabilityexperimental
Maintainer[email protected]
Safe HaskellNone

Data.Array.MArray

Contents

Description

An overloaded interface to mutable arrays. For array types which can be used with this interface, see Data.Array.IO, Data.Array.ST, and Data.Array.Storable.

Synopsis

Class of mutable array types

class Monad m => MArray a e m whereSource

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.

Methods

getBounds :: Ix i => a i e -> m (i, i)Source

Returns the bounds of 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.

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 Ix class and operations

module Data.Ix

Constructing mutable arrays

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.

Reading and writing mutable arrays

readArray :: (MArray a e m, Ix i) => a i e -> i -> m eSource

Read an element from a mutable array

writeArray :: (MArray a e m, Ix i) => a i e -> i -> e -> m ()Source

Write an element in a mutable array

Derived arrays

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.

Deconstructing mutable arrays

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.

Conversions between mutable and immutable arrays

freeze :: (Ix i, MArray a e m, IArray b e) => a i e -> m (b i e)Source

Converts a mutable array (any instance of MArray) to an immutable array (any instance of IArray) by taking a complete copy of it.

unsafeFreeze :: (Ix i, MArray a e m, IArray b e) => a i e -> m (b i e)Source

Deprecated: Please import from Data.Array.Unsafe instead; This will be removed in the next release

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.

thaw :: (Ix i, IArray a e, MArray b e m) => a i e -> m (b i e)Source

Converts an immutable array (any instance of IArray) into a mutable array (any instance of MArray) by taking a complete copy of it.

unsafeThaw :: (Ix i, IArray a e, MArray b e m) => a i e -> m (b i e)Source

Deprecated: Please import from Data.Array.Unsafe instead; This will be removed in the next release

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.