Type.RowList

class ListToRow :: forall k. RowList k -> Row k -> Constraintclass ListToRow list row | 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 RowListRemove :: forall k. Symbol -> RowList k -> RowList k -> Constraintclass RowListRemove label input output | 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 tailOutput (Cons key head tailOutput) output) => RowListRemove label (Cons key head tail) output

class RowListSet :: forall k. Symbol -> k -> RowList k -> RowList k -> Constraintclass RowListSet label typ input output | label typ input -> output

Add a label to a RowList after removing other occurences.

Instances

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

class RowListNub :: forall k. RowList k -> RowList k -> Constraintclass RowListNub input output | input -> output

Remove label duplicates, keeps earlier occurrences.

Instances

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

class RowListAppend :: forall k. RowList k -> RowList k -> RowList k -> Constraintclass RowListAppend lhs rhs out | lhs rhs -> out

Instances

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

data RowList :: Type -> Type

A type level list representation of a row of types.

data Nil :: forall (k :: Type). RowList k

The empty RowList.

data Cons :: forall (k :: Type). Symbol -> k -> RowList k -> RowList k

Constructs a new RowList from a label, a type, and an existing tail RowList. E.g: Cons "x" Int (Cons "y" Int Nil).

class RowToList (row :: Row k) (list :: RowList k) | 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.