Type.Prelude

data True :: Boolean

The 'True' boolean type.

data False :: Boolean

The 'False' boolean type.

data BProxy (bool :: Boolean)

Value proxy for Boolean types

Constructors

• BProxy

class IsBoolean (bool :: Boolean)  where

Class for reflecting a type level Boolean at the value level

Members

• reflectBoolean :: BProxy bool -> Boolean

Instances

• IsBoolean True
• IsBoolean False

reifyBoolean :: forall r. Boolean -> (forall o. IsBoolean o => BProxy o -> r) -> r

Use a value level Boolean as a type-level Boolean

data Boolean :: Type

The Boolean kind provides True/False types at the type level

data OProxy (ordering :: Ordering)

Value proxy for Ordering types

Constructors

• OProxy

data LT :: Ordering

The 'less than' ordering type.

data GT :: Ordering

The 'greater than' ordering type.

data EQ :: Ordering

The 'equal to' ordering type.

class IsOrdering (ordering :: Ordering)  where

Class for reflecting a type level Ordering at the value level

Members

• reflectOrdering :: OProxy ordering -> Ordering

Instances

• IsOrdering LT
• IsOrdering EQ
• IsOrdering GT

reifyOrdering :: forall r. Ordering -> (forall o. IsOrdering o => OProxy o -> r) -> r

Use a value level Ordering as a type-level Ordering

data Ordering :: Type

The Ordering kind represents the three possibilites of comparing two types of the same kind: LT (less than), EQ (equal to), and GT (greater than).

data SProxy (sym :: Symbol)

A value-level proxy for a type-level symbol.

Constructors

• SProxy

class Append (left :: Symbol) (right :: Symbol) (appended :: Symbol) | left right -> appended, right appended -> left, appended left -> right

Compiler solved type class for appending Symbols together.

class Compare (left :: Symbol) (right :: Symbol) (ordering :: Ordering) | left right -> ordering

Compiler solved type class for comparing two Symbols. Produces an Ordering.

class IsSymbol (sym :: Symbol)  where

A class for known symbols

Members

• reflectSymbol :: SProxy sym -> String

reifySymbol :: forall r. String -> (forall sym. IsSymbol sym => SProxy sym -> r) -> r

compare :: forall o r l. Compare l r o => SProxy l -> SProxy r -> OProxy o

append :: forall o r l. Append l r o => SProxy l -> SProxy r -> SProxy o

class TypeEquals a b | a -> b, b -> a where

This type class asserts that types a and b are equal.

The functional dependencies and the single instance below will force the two type arguments to unify when either one is known.

Note: any instance will necessarily overlap with refl below, so instances of this class should not be defined in libraries.

Members

• to :: a -> b
• from :: b -> a

Instances

• TypeEquals a a

data Proxy a

Value proxy for kind Type types.

Constructors

• Proxy

Instances

• Eq (Proxy a)
• Functor Proxy
• Ord (Proxy a)
• Applicative Proxy
• Apply Proxy
• Bind Proxy
• BooleanAlgebra (Proxy a)
• Bounded (Proxy a)
• CommutativeRing (Proxy a)
• Discard (Proxy a)
• HeytingAlgebra (Proxy a)
• Monad Proxy
• Ring (Proxy a)
• Semigroup (Proxy a)
• Semiring (Proxy a)
• Show (Proxy a)

data RProxy (row :: Row Type)

A proxy data type whose type parameter is a type of kind # Type (a row of types).

Commonly used for specialising a function with a quantified type. For example, suppose we have an identity function for records of type:

recordIdentity :: forall row . RProxy row -> Record row -> Record row
recordIdentity _ rec = rec

Then applying this function to an RProxy with a specialised type allows us to specify a concrete type for row:

:t recordIdentity (RProxy :: RProxy ( x :: Int, y :: Int ))
{ x :: Int, y :: Int } -> { x :: Int, y :: Int }

Here row has been specialised to ( x :: Int, y :: Int ).

Constructors

• RProxy

class Lacks (label :: Symbol) (row :: Row Type) 

The Lacks type class asserts that a label does not occur in a given row.

class Union (left :: Row Type) (right :: Row Type) (union :: Row Type) | left right -> union, right union -> left, union left -> right

The Union type class is used to compute the union of two rows of types (left-biased, including duplicates).

The third type argument represents the union of the first two.

data RLProxy (rowlist :: RowList)

A proxy data type whose type parameter is a type of kind RowList.

Commonly used for specialising a function with a quantified type.

Constructors

• RLProxy

class ListToRow (list :: RowList) (row :: Row Type) | list -> row

Convert a RowList to a row of types. The inverse of this operation is RowToList.

Instances

• ListToRow Nil ()
• (ListToRow tail tailRow, Cons label ty tailRow row) => ListToRow (Cons label ty tail) row

class RowToList (row :: Row Type) (list :: RowList) | row -> list

Compiler solved type class for generating a RowList from a closed row of types. Entries are sorted by label and duplicates are preserved in the order they appeared in the row.