Control.Monad.Memo.Array (original) (raw)

Contents

• ArrayCache for boxed types
• ArrayCache for unboxed types
• Generic function for ArrayCache

Description

ArrayCache - mutable-array-based ([IO](/packages/archive/base/4.6.0.1/doc/html/System-IO.html#t:IO) and [ST](/packages/archive/base/4.6.0.1/doc/html/Control-Monad-ST-Safe.html#t:ST) hosted) [MonadCache](Control-Monad-Memo-Class.html#t:MonadCache)

Very fast memoization cache. Unfortunatelly it cannot suit every case (see limitations), but if you can use it, please do: it is generally an order of magnitude faster than [Map](Data.html#t:Map)-based [Memo](Control-Monad-Trans-Memo-Map.html#t:Memo), especially unboxed version - try to use it whenever you can.

Limitations: Since [MArray](/packages/archive/array/0.4.0.1/doc/html/Data-Array-Base.html#t:MArray) is used as [MonadCache](Control-Monad-Memo-Class.html#t:MonadCache) the key range must be known beforehand and the array is allocated before the first call. It is therefore most suitable for the cases when the distribution of possible key values is within reasonable range and is rather dense (the best case: all values withing some range will be used). If this is the case then [MArray](/packages/archive/array/0.4.0.1/doc/html/Data-Array-MArray.html#t:MArray) has O(1) for both lookup and update operations. In addition unboxed [UArrayCache](Control-Monad-Memo-Array.html#t:UArrayCache) can only store unboxed types (but it does it very efficiently).

Synopsis

• type family Array m :: * -> * -> *
• type ArrayCache k e m = Cache (Array m) k e m
• class MaybeLike e v => ArrayMemo v e | v -> e
• evalArrayMemo :: (Ix k, MArray (Array m) e m, ArrayMemo v e) => ArrayCache k e m a -> (k, k) -> m a
• runArrayMemo :: (Ix k, MArray (Array m) e m, ArrayMemo v e) => ArrayCache k e m a -> (k, k) -> m (a, Array m k e)
• type family UArray m :: * -> * -> *
• type UArrayCache k e m = Cache (UArray m) k e m
• class MaybeLike e v => UArrayMemo v e | v -> e
• evalUArrayMemo :: (Ix k, MArray (UArray m) e m, UArrayMemo v e) => UArrayCache k e m a -> (k, k) -> m a
• runUArrayMemo :: (Ix k, MArray (UArray m) e m, UArrayMemo v e) => UArrayCache k e m a -> (k, k) -> m (a, UArray m k e)
• newtype Container arr = Container {
  • toArray :: arr
    }
• type Cache arr k e = ReaderCache (Container (arr k e))
• genericEvalArrayMemo :: (Ix k, MaybeLike e v, MArray arr e m) => Cache arr k e m a -> (k, k) -> m a
• genericRunArrayMemo :: (Ix k, MaybeLike e v, MArray arr e m) => Cache arr k e m a -> (k, k) -> m (a, arr k e)

ArrayCache for boxed types

type family Array m :: * -> * -> *Source

A family of boxed arrays

class MaybeLike e v => ArrayMemo v e | v -> eSource

This is just to be able to infer the type of the [ArrayCache](Control-Monad-Memo-Array.html#t:ArrayCache) element

Type families could be used instead but due to the bug in 7.4.* we cannot use them here

evalArrayMemoSource

Evaluate computation using boxed array

Key range should cover all possible keys used in computation otherwise not in range error is generated by array

runArrayMemoSource

Arguments

Evaluate computation and the final content of array cache using boxed array

Key range should cover all possible keys used in computation otherwise not in range error is generated by array

ArrayCache for unboxed types

type family UArray m :: * -> * -> *Source

A family of unboxed arrays

class MaybeLike e v => UArrayMemo v e | v -> eSource

This is just to be able to infer the type of the [UArrayCache](Control-Monad-Memo-Array.html#t:UArrayCache) element

Type families could be used instead but due to the bug in 7.4.* we cannot use them here

evalUArrayMemoSource

Evaluate computation using unboxed array

Key range should cover all possible keys used in computation otherwise not in range error is generated by array

runUArrayMemoSource

Evaluate computation and the final content of array cache using unboxed array

Key range should cover all possible keys used in computation otherwise not in range error is generated by array

Generic function for ArrayCache