Type.Row

data RProxy (row :: Row Type)

Constructors

• RProxy

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 ()
• RowListRemove label Nil Nil
• RowListNub Nil Nil
• (TypeEquals (RLProxy rhs) (RLProxy out)) => RowListAppend Nil rhs out

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

Instances

• (ListToRow tail tailRow, RowCons label ty tailRow row) => ListToRow (Cons label ty tail) row
• (RowListRemove label tail tailOutput, Equals label key eq, If eq (RLProxy tailOutput) (RLProxy (Cons key head tailOutput)) (RLProxy output)) => RowListRemove label (Cons key head tail) output
• (TypeEquals (SProxy label) (SProxy label'), TypeEquals typ typ', RowListRemove label input lacking) => RowListSet label typ input (Cons label' typ' lacking)
• (TypeEquals (SProxy label) (SProxy label'), TypeEquals head head', TypeEquals (RLProxy nubbed) (RLProxy nubbed'), RowListRemove label tail removed, RowListNub removed nubbed) => RowListNub (Cons label head tail) (Cons label' head' nubbed')
• (RowListAppend tail rhs out', TypeEquals (RLProxy (Cons label head out')) (RLProxy out)) => RowListAppend (Cons label head tail) rhs out

data RLProxy (rowList :: RowList)

Constructors

• RLProxy

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

class RowListRemove (label :: Symbol) (input :: RowList) (output :: RowList) | label input -> output

Remove all occurences of a given label from a RowList

Instances

• RowListRemove label Nil Nil
• (RowListRemove label tail tailOutput, Equals label key eq, If eq (RLProxy tailOutput) (RLProxy (Cons key head tailOutput)) (RLProxy output)) => RowListRemove label (Cons key head tail) output

class RowListSet (label :: Symbol) (typ :: Type) (input :: RowList) (output :: RowList) | label typ input -> output

Add a label to a RowList after removing other occurences.

Instances

• (TypeEquals (SProxy label) (SProxy label'), TypeEquals typ typ', RowListRemove label input lacking) => RowListSet label typ input (Cons label' typ' lacking)

class RowListNub (input :: RowList) (output :: RowList) | input -> output

Remove label duplicates, keeps earlier occurrences.

Instances

• RowListNub Nil Nil
• (TypeEquals (SProxy label) (SProxy label'), TypeEquals head head', TypeEquals (RLProxy nubbed) (RLProxy nubbed'), RowListRemove label tail removed, RowListNub removed nubbed) => RowListNub (Cons label head tail) (Cons label' head' nubbed')

class RowListAppend (lhs :: RowList) (rhs :: RowList) (out :: RowList) | lhs rhs -> out

Instances

• (TypeEquals (RLProxy rhs) (RLProxy out)) => RowListAppend Nil rhs out
• (RowListAppend tail rhs out', TypeEquals (RLProxy (Cons label head out')) (RLProxy out)) => RowListAppend (Cons label head tail) rhs out