Data.Function.Variadic

Decomposition and creation of functions

class (ConstructFunction args r ~ f, DeconstructFunction f ~ '(args, r)) => Function f args r argC where

Toolkit for creating and transforming functions with a variable number of arguments. Its parameters are function, list of its arguments, its result, and argC that constraints all arguments of the function.

Methods

createFunction

Arguments

:: proxy argC

Required for unambiguous choice of Function instance

-> (forall a. argC a => acc -> a -> acc)

Combine arguments with accumulator

-> (acc -> r)

Make result of the function

-> acc

Accumulator

-> f

Create a new function

Example usage

>>> printf :: Function Show f args String => f
>>> printf = createFunction (Proxy :: Proxy Show) (\acc a -> acc <> show a) id ""
>>> printf "hello" () :: String
"hello()"

transformFunction

Arguments

:: proxy argC

Required for unambiguous choice of the Function instance

-> (forall a. argC a => acc -> a -> acc)

Combine arguments with accumulator

-> (acc -> r0 -> r)

Create result of the f function using accumulator and the result of the function to transform

-> acc

Accumulator

-> ConstructFunction args r0

The function to transform

-> f

The new function

Create a function with the same arguments as given one but may have a different result.

Instances

'('[] :: [Type], r) ~ DeconstructFunction r => Function r ('[] :: [Type]) r argC

Defined in Data.Function.Variadic

Methods

createFunction :: proxy argC -> (forall a. argC a => acc -> a -> acc) -> (acc -> r) -> acc -> r

transformFunction :: proxy argC -> (forall a. argC a => acc -> a -> acc) -> (acc -> r0 -> r) -> acc -> ConstructFunction '[] r0 -> r

(Function f args r argC, argC a) => Function (a -> f) (a ': args) r argC

Defined in Data.Function.Variadic

Methods

createFunction :: proxy argC -> (forall a0. argC a0 => acc -> a0 -> acc) -> (acc -> r) -> acc -> a -> f

transformFunction :: proxy argC -> (forall a0. argC a0 => acc -> a0 -> acc) -> (acc -> r0 -> r) -> acc -> ConstructFunction (a ': args) r0 -> a -> f

type family ConstructFunction (args :: [Type]) (r :: Type) where ...

Given the types of function arguments and its result, make a type of a function.

Equations

ConstructFunction '[] r = r

ConstructFunction (a ': args) r = a -> ConstructFunction args r

type family DeconstructFunction (f :: Type) :: ([Type], Type) where ...

Extract list of arguments and the result from the function.

Equations

DeconstructFunction (a -> f) = MapFst ((:) a) (DeconstructFunction f)

DeconstructFunction x = '('[], x)

Helper classes for argument constraints

class EmptyConstraint a

When the arguments are not constrained, use this as the argC parameter of Function.

Instances

EmptyConstraint (a :: k)

Defined in Data.Function.Variadic

class (f x, g x) => (f & g) (x :: k)

Combine constraints. For example, Function f args x (Show & Num).

Instances

(f x, g x) => ((f :: k -> Constraint) & (g :: k -> Constraint)) (x :: k)

Defined in Data.Function.Variadic