Type.Row

class RowLacking (entry :: Type) (key :: Symbol) (typ :: Type) (row :: Row Type) | entry typ -> key row

If you get "No type class instance was found" for this class, then your row shouldn't contain the label key.

Instances

• RowLacking entry key entry row

class RowLacks (key :: Symbol) (row :: Row Type) 

Encodes the constraint that a given row does not contain a specific key.

data RowList :: Type

A type-level list representation of a row

data Nil :: RowList

Instances

• ListToRow Nil ()

data Cons :: Symbol -> Type -> RowList -> RowList

Instances

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

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

Extract the collection of entries in a closed row of types. The list of entries is sorted by label and preserves duplicates. The inverse of this operation is ListToRow. Solved by the compiler.

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