| Portability | non-portable |
|---|---|
| Stability | experimental |
| Maintainer | [email protected] |
Database.HaskellDB.HDBRec
Contents
Description
This is a replacement for some of TREX.
- data RecNil = RecNil
- data RecCons f a b = RecCons a b
- type Record r = RecNil -> r
- emptyRecord :: Record RecNil
- (.=.) :: l f a -> a -> Record (RecCons f a RecNil)
- (#) :: Record (RecCons f a RecNil) -> (b -> c) -> b -> RecCons f a c
- class FieldTag f where
- class HasField f r
- class Select f r a | f r -> a where
- (!) :: r -> f -> a
- class SetField f r a
- setField :: SetField f r a => l f a -> a -> r -> r
- class RecCat r1 r2 r3 | r1 r2 -> r3 where
- recCat :: r1 -> r2 -> r3
- class ShowLabels r where
- recordLabels :: r -> [String]
- class ShowRecRow r where
- showRecRow :: r -> [(String, ShowS)]
- class ReadRecRow r where
- readRecRow :: [(String, String)] -> [(r, [(String, String)])]
Record types
The empty record.
Constructors
| RecNil |
Constructor that adds a field to a record. f is the field tag, a is the field value and b is the rest of the record.
Constructors
| RecCons a b |
Instances
Record construction
emptyRecord :: Record RecNilSource
The empty record
Creates one-field record from a label and a value
Arguments
| :: Record (RecCons f a RecNil) | Field to add |
| -> (b -> c) | Rest of record |
| -> b -> RecCons f a c | New record |
Adds the field from a one-field record to another record.
Labels
Class for field labels.
Record predicates and operations
The record r has the field f if there is an instance of
HasField f r.
class Select f r a | f r -> a whereSource
Methods
Field selection operator. It is overloaded so that users (read HaskellDB) can redefine it for things with phantom record types.
Instances
| SelectField f r a => Select (l f a) (Record r) a | |
| HasField f r => Select (Attr f a) (Rel r) (Expr a) | Field selection operator. It is overloaded to work for both
relations in a query and the result of a query.
That is, it corresponds to both |
Showing and reading records
class ShowLabels r whereSource
Methods
recordLabels :: r -> [String]Source
Instances
| ShowLabels RecNil | |
| ShowLabels r => ShowLabels (Record r) | |
| (FieldTag f, ShowLabels r) => ShowLabels (RecCons f a r) |
class ShowRecRow r whereSource
Convert a record to a list of label names and field values.
Methods
showRecRow :: r -> [(String, ShowS)]Source
Instances
| ShowRecRow RecNil | |
| ShowRecRow r => ShowRecRow (Record r) | |
| (FieldTag a, Show b, ShowRecRow c) => ShowRecRow (RecCons a b c) |
class ReadRecRow r whereSource
Methods
readRecRow :: [(String, String)] -> [(r, [(String, String)])]Source
Convert a list of labels and strins representating values to a record.
Instances
| ReadRecRow RecNil | |
| (FieldTag a, Read b, ReadRecRow c) => ReadRecRow (RecCons a b c) |