Copyright	HWT Group (c) 2003, [email protected]
License	BSD-style
Maintainer	[email protected]
Stability	experimental
Portability	non-portable
Safe Haskell	None
Language	Haskell98

Database.HaskellDB.HDBRec

Contents

Record types
Record construction
Labels
Record predicates and operations
Showing and reading records

Description

This is a replacement for some of TREX.

Synopsis

Record types

data RecNil Source

The empty record.

Constructors

RecNil

Instances

Eq RecNil
Ord RecNil
Read RecNil
Show RecNil
ReadRecRow RecNil
ShowRecRow RecNil
ShowLabels RecNil
ToPrimExprs RecNil
RelToRec RecNil
ExprTypes RecNil
ConstantRecord RecNil RecNil
ProjectRec RecNil RecNil
InsertRec RecNil RecNil
GetRec RecNil RecNil
RecCat RecNil r r
HasField f r => HasField f (Record r)
SetField f r a => SetField f (Record r) a
Eq r => Eq (Record r)
Ord r => Ord (Record r)
ReadRecRow r => Read (Record r)
Show r => Show (Record r)
ShowRecRow r => ShowRecRow (Record r)
ShowLabels r => ShowLabels (Record r)
ExprTypes r => ExprTypes (Record r)
ConstantRecord r cr => ConstantRecord (Record r) (Record cr)
RecCat r1 r2 r3 => RecCat (Record r1) (Record r2) (Record r3)
SelectField f r a => Select (l f a) (Record r) a

data RecCons f a b Source

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

HasField f r => HasField f (RecCons g a r)
HasField f (RecCons f a r)
SetField f r a => SetField f (RecCons g b r) a
SetField f (RecCons f a r) a
(Eq a, Eq b) => Eq (RecCons f a b)
(Ord a, Ord b) => Ord (RecCons f a b)
(FieldTag a, Read b, ReadRecRow c) => Read (RecCons a b c)
(FieldTag a, Show b, ShowRecRow c) => Show (RecCons a b c)
(FieldTag a, Read b, ReadRecRow c) => ReadRecRow (RecCons a b c)
(FieldTag a, Show b, ShowRecRow c) => ShowRecRow (RecCons a b c)
(FieldTag f, ShowLabels r) => ShowLabels (RecCons f a r)
(ExprC e, ToPrimExprs r) => ToPrimExprs (RecCons l (e a) r)
(RelToRec rest, FieldTag f) => RelToRec (RecCons f (Expr a) rest)
(ExprType e, ExprTypes r) => ExprTypes (RecCons f e r)
RecCat r1 r2 r3 => RecCat (RecCons f a r1) r2 (RecCons f a r3)
(ShowConstant a, ConstantRecord r cr) => ConstantRecord (RecCons f a r) (RecCons f (Expr a) cr)
(ProjectExpr e, ProjectRec r er) => ProjectRec (RecCons f (e a) r) (RecCons f (Expr a) er)
(InsertExpr e, InsertRec r er) => InsertRec (RecCons f (e a) r) (RecCons f (Expr a) er)
(GetValue a, GetRec er vr) => GetRec (RecCons f (Expr a) er) (RecCons f a vr)

type Record r = RecNil -> r Source

The type used for records. This is a function that takes a RecNil so that the user does not have to put a RecNil at the end of every record.

Record construction

emptyRecord :: Record RecNil Source

The empty record

(.=.) infix 6 Source

Arguments

:: l f a	Label
-> a	Value
-> Record (RecCons f a RecNil)	New record

Creates one-field record from a label and a value

(#) infixr 5 Source

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 FieldTag f where Source

Class for field labels.

Methods

fieldName :: f -> String Source

Gets the name of the label.

Record predicates and operations

class HasField f r Source

The record r has the field f if there is an instance of HasField f r.

Instances

HasField f r => HasField f (Record r)
HasField f r => HasField f (RecCons g a r)
HasField f (RecCons f a r)

class Select f r a | f r -> a where Source

Methods

(!) :: r -> f -> a infix 9 Source

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 `!` and `!.` from the original HaskellDB. An overloaded operator was selected because users (and the developers) always forgot to use !. instead of ! on query results.

class SetField f r a Source

Minimal complete definition

setField_

Instances

SetField f r a => SetField f (Record r) a
SetField f r a => SetField f (RecCons g b r) a
SetField f (RecCons f a r) a

setField :: SetField f r a => l f a -> a -> r -> r Source

class RecCat r1 r2 r3 | r1 r2 -> r3 where Source

Methods

recCat :: r1 -> r2 -> r3 Source

Concatenates two records.

Instances

RecCat RecNil r r
RecCat r1 r2 r3 => RecCat (Record r1) (Record r2) (Record r3)
RecCat r1 r2 r3 => RecCat (RecCons f a r1) r2 (RecCons f a r3)

Showing and reading records

class ShowLabels r where Source

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 where Source

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 where Source

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)