A label

This class gives the string associated with a type-level symbol. There are instances of the class for every concrete literal: "hello", etc.

Since: base-4.7.0.0

Are all of the labels in this Row unique?

A convenient way to provide common, easy constraints

The variant type.

A record with row r.

The kind of rows. This type is only used as a datakind. A row is a typelevel entity telling us which symbols are associated with which types.

Type level version of empty

A lower fixity operator for type equality

Alias for (r .! l) ≈ a. It is a class rather than an alias, so that it can be partially applied.

Is the first row a subset of the second? Or, does the second row contain every binding that the first one does?

Alias for .\. It is a class rather than an alias, so that it can be partially applied.

Does the row lack (i.e. it does not have) the specified label?

Type level Row append

The minimum join of the two rows.

Type level Row difference. That is, l .\\ r is the row remaining after removing any matching elements of r from l.

The overwriting union, where the left row overwrites the types of the right row where the labels overlap.

Any structure over two rows in which the elements of each row satisfy some constraints can be metamorphized into another structure over both of the rows.

Any structure over a row in which every element is similarly constrained can be metamorphized into another structure over the same row.

FreeForall can be used when a Forall constraint is necessary but there is no particular constraint we care about.

FreeForall can be used when a BiForall constraint is necessary but there is no particular constraint we care about.

A Var and a Rec can combine if their rows line up properly. Given a Variant along with a Record of functions from each possible value of the variant to a single output type, apply the correct function to the value in the variant.

The same as switch but with the argument order reversed

The empty record

A type level way to create a singleton Row.

The singleton record

A pattern for the singleton record; can be used to both destruct a record when in a pattern position or construct one in an expression position.

Type level Row element removal

Record restriction. Remove the label l from the record.

Type level label fetching

Record selection

Record disjoint union (commutative)

A type synonym for disjointness.

A pattern version of record union, for use in pattern matching.

Record overwrite.

The operation r .// r' creates a new record such that:

• Any label that is in both r and r' is in the resulting record with the type and value given by the fields in r,
• Any label that is only found in r is in the resulting record.
• Any label that is only found in r' is in the resulting record.

This can be thought of as r "overwriting" r'.

A pattern for variants; can be used to both destruct a variant when in a pattern position or construct one in an expression position.

Make the variant arbitrarily more diverse.

A Variant with no options is uninhabited.

Convert a variant into either the value at the given label or a variant without that label. This is the basic variant destructor.

A version of trial that ignores the leftover variant.

A trial over multiple types

Return a list of the labels in a row type.