| Safe Haskell | None |
|---|---|
| Language | Haskell98 |
Data.Function.Memoize
Description
A function memoization library.
This includes a class for memoizable argument types and a Template Haskell expander for deriving instances of the class.
Note that most memoization in this style relies on assumptions about the implementation of non-strictness (as laziness) that are not guaranteed by the semantics. However, it appears to work.
Synopsis
- class Memoizable a where
- memoize :: (a -> v) -> a -> v
- memoize2 :: (Memoizable a, Memoizable b) => (a -> b -> v) -> a -> b -> v
- memoize3 :: (Memoizable a, Memoizable b, Memoizable c) => (a -> b -> c -> v) -> a -> b -> c -> v
- memoize4 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d) => (a -> b -> c -> d -> v) -> a -> b -> c -> d -> v
- memoize5 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e) => (a -> b -> c -> d -> e -> v) -> a -> b -> c -> d -> e -> v
- memoize6 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e, Memoizable f) => (a -> b -> c -> d -> e -> f -> v) -> a -> b -> c -> d -> e -> f -> v
- memoize7 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e, Memoizable f, Memoizable g) => (a -> b -> c -> d -> e -> f -> g -> v) -> a -> b -> c -> d -> e -> f -> g -> v
- memoFix :: Memoizable a => ((a -> v) -> a -> v) -> a -> v
- memoFix2 :: (Memoizable a, Memoizable b) => ((a -> b -> v) -> a -> b -> v) -> a -> b -> v
- memoFix3 :: (Memoizable a, Memoizable b, Memoizable c) => ((a -> b -> c -> v) -> a -> b -> c -> v) -> a -> b -> c -> v
- memoFix4 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d) => ((a -> b -> c -> d -> v) -> a -> b -> c -> d -> v) -> a -> b -> c -> d -> v
- memoFix5 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e) => ((a -> b -> c -> d -> e -> v) -> a -> b -> c -> d -> e -> v) -> a -> b -> c -> d -> e -> v
- memoFix6 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e, Memoizable f) => ((a -> b -> c -> d -> e -> f -> v) -> a -> b -> c -> d -> e -> f -> v) -> a -> b -> c -> d -> e -> f -> v
- memoFix7 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e, Memoizable f, Memoizable g) => ((a -> b -> c -> d -> e -> f -> g -> v) -> a -> b -> c -> d -> e -> f -> g -> v) -> a -> b -> c -> d -> e -> f -> g -> v
- traceMemoize :: (Memoizable a, Show a) => (a -> b) -> a -> b
- memoizeFinite :: (Enum a, Bounded a) => (a -> v) -> a -> v
- deriveMemoizable :: Name -> Q [Dec]
- deriveMemoizableParams :: Name -> [Int] -> Q [Dec]
- deriveMemoize :: Name -> ExpQ
Memoization class
class Memoizable a where Source #
A memoization class. An instance Memoizable TT means that that memoize method can memoize for
parameters of type T.
Instances
Operations
Higher-arity memoize
memoize2 :: (Memoizable a, Memoizable b) => (a -> b -> v) -> a -> b -> v Source #
Memoize a two argument function
memoize3 :: (Memoizable a, Memoizable b, Memoizable c) => (a -> b -> c -> v) -> a -> b -> c -> v Source #
Memoize a three argument function
memoize4 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d) => (a -> b -> c -> d -> v) -> a -> b -> c -> d -> v Source #
Memoize a four argument function
memoize5 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e) => (a -> b -> c -> d -> e -> v) -> a -> b -> c -> d -> e -> v Source #
Memoize a five argument function
memoize6 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e, Memoizable f) => (a -> b -> c -> d -> e -> f -> v) -> a -> b -> c -> d -> e -> f -> v Source #
Memoize a six argument function
memoize7 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e, Memoizable f, Memoizable g) => (a -> b -> c -> d -> e -> f -> g -> v) -> a -> b -> c -> d -> e -> f -> g -> v Source #
Memoize a seven argument function
Memoizing open recursion
memoFix :: Memoizable a => ((a -> v) -> a -> v) -> a -> v Source #
Memoizes the least fixed point of a function. This is like
fix, but it passes the fixed function a memoized
version of itself, so this memoizes using all recursive calls as well.
memoFix2 :: (Memoizable a, Memoizable b) => ((a -> b -> v) -> a -> b -> v) -> a -> b -> v Source #
Two argument version of memoFix.
memoFix3 :: (Memoizable a, Memoizable b, Memoizable c) => ((a -> b -> c -> v) -> a -> b -> c -> v) -> a -> b -> c -> v Source #
Three argument version of memoFix.
memoFix4 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d) => ((a -> b -> c -> d -> v) -> a -> b -> c -> d -> v) -> a -> b -> c -> d -> v Source #
Four argument version of memoFix.
memoFix5 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e) => ((a -> b -> c -> d -> e -> v) -> a -> b -> c -> d -> e -> v) -> a -> b -> c -> d -> e -> v Source #
Five argument version of memoFix.
memoFix6 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e, Memoizable f) => ((a -> b -> c -> d -> e -> f -> v) -> a -> b -> c -> d -> e -> f -> v) -> a -> b -> c -> d -> e -> f -> v Source #
Six argument version of memoFix.
memoFix7 :: (Memoizable a, Memoizable b, Memoizable c, Memoizable d, Memoizable e, Memoizable f, Memoizable g) => ((a -> b -> c -> d -> e -> f -> g -> v) -> a -> b -> c -> d -> e -> f -> g -> v) -> a -> b -> c -> d -> e -> f -> g -> v Source #
Seven argument version of memoFix.
Tracing memoization
traceMemoize :: (Memoizable a, Show a) => (a -> b) -> a -> b Source #
Give a one-argument function whose argument satisfies Show,
this memoizes the function such that the argument is shown (using
trace) only when the function has to be applied, as
opposed to when the answer is available in the memo cache.
For making instances for finite types
memoizeFinite :: (Enum a, Bounded a) => (a -> v) -> a -> v Source #
Can be used to memoize over any "finite" type satisfying
Enum and Bounded. This builds a binary search tree, treating
the memoized type as isomorphic to a range of Int, so it will be
only as efficient as toEnum, fromEnum, succ, and pred.
This can be used to make instances for finite types. For example, the
instances for Int and Char are declared as:
instance Memoizable Int where memoize = memoizeFinite instance Memoizable Char where memoize = memoizeFinite
Deriving Memoizable
deriveMemoizable :: Name -> Q [Dec] Source #
To derive Memoizable instances for the given data types.
In the simplest usage, to derive Memoizable for an algebraic
datatype named T, write:
deriveMemoizable ''T
This assumes that all the type parameters of T that are not
annotated with a kind other than * should be listed as requiring
Memoizable instances in the instance context. For example, given
a data type declared as
data T a (b :: * -> *) c = ...
the generated instance will look like
instance (Memoizablea,Memoizablec) =>Memoizable(T a b c) where ...
For more precise control over the context, use
deriveMemoizableParams.
N.B.: The TemplateHaskell language extension must be enabled to use
this function.
deriveMemoizableParams :: Name -> [Int] -> Q [Dec] Source #
Like deriveMemoizable but takes a second argument, which is a list
of Ints to specify which type parameters of the type should be
mentioned in the context. For example, given the same definition for
T as above, we can write
deriveMemoizableParams ''T [3]
to leave the first parameter of T out of the context and show
only the third, yielding the instance
instanceMemoizablec =>Memoizable(T a b c) where ...
N.B.: The TemplateHaskell language extension must be enabled to use
this function.
deriveMemoize :: Name -> ExpQ Source #
In cases where neither deriveMemoizable nor
deriveMemoizableParams can figure out the right context for an
instance declaration, one can declare the instance manually and use
this function to derive the method body for memoize. For example,
suppose that a data type T is defined as:
data T a b = T (a -> Bool) b
For T a b to be memoizable, a -> Bool must be, and based on the
instance for '(->)', this means that a must satisfy
Bounded and Enum, so deriveMemoizable cannot build the right
context for the Memoizable instance. Instead, one can write:
instance (Enuma,Boundeda,Memoizableb) =>Memoizable(T a b) where memoize = $(deriveMemoize ''T)