Z.Data.JSON.Value

This module provides definition and parsers for JSON Values, a Haskell JSON representation. The parsers is designed to comply with rfc8258, notable pitfalls are:

• The numeric representation use Scientific, which impose a limit on number's exponent part(limited to Int).
• Unescaped control characters(<=0x1F) are NOT accepted, (different from aeson).
• Only 0x20, 0x09, 0x0A, 0x0D are valid JSON whitespaces, skipSpaces from this module is different from skipSpaces.
• A JSON document shouldn't have trailing characters except whitespaces describe above, see parseValue' and parseValueChunks'.
• Objects are represented as key-value vectors, key order and duplicated keys are preserved for further processing.

Note that rfc8258 doesn't enforce unique key in objects, it's up to users to decided how to deal with key duplication, e.g. prefer first or last key, see withFlatMap or withFlatMapR for example.

There's no lazy parsers here, every pieces of JSON document will be parsed into a normal form Value. Object and Arrays payloads are packed into Vectors to avoid accumulating lists in memory. Read more about why no lazy parsing is needed.

Value type

data Value

A JSON value represented as a Haskell value.

The Object's payload is a key-value vector instead of a map, which parsed directly from JSON document. This design choice has following advantages:

• Allow different strategies handling duplicated keys.
• Allow different Map type to do further parsing, e.g. FlatMap
• Roundtrip without touching the original key-value order.
• Save time if constructing map is not neccessary, e.g. using a linear scan to find a key if only that key is needed.

Constructors

Object !(Vector (Text, Value))

Array !(Vector Value)

String !Text

Number !Scientific

Bool !Bool

Null

Instances

Eq Value

Defined in Z.Data.JSON.Value

Methods

(==) :: Value -> Value -> Bool

(/=) :: Value -> Value -> Bool

Ord Value

Defined in Z.Data.JSON.Value

Methods

compare :: Value -> Value -> Ordering

(<) :: Value -> Value -> Bool

(<=) :: Value -> Value -> Bool

(>) :: Value -> Value -> Bool

(>=) :: Value -> Value -> Bool

max :: Value -> Value -> Value

min :: Value -> Value -> Value

Show Value

Defined in Z.Data.JSON.Value

Methods

showsPrec :: Int -> Value -> ShowS

show :: Value -> String

showList :: [Value] -> ShowS

Generic Value

Defined in Z.Data.JSON.Value

Associated Types

type Rep Value :: Type -> Type

Methods

from :: Value -> Rep Value x

to :: Rep Value x -> Value

Arbitrary Value

Defined in Z.Data.JSON.Value

Methods

arbitrary :: Gen Value

shrink :: Value -> [Value]

NFData Value

Defined in Z.Data.JSON.Value

Methods

rnf :: Value -> ()

Print Value

Defined in Z.Data.JSON.Value

Methods

toUTF8BuilderP :: Int -> Value -> Builder ()

JSON Value

Defined in Z.Data.JSON.Base

Methods

fromValue :: Value -> Converter Value

toValue :: Value -> Value

encodeJSON :: Value -> Builder ()

type Rep Value

Defined in Z.Data.JSON.Value

type Rep Value = D1 ('MetaData "Value" "Z.Data.JSON.Value" "Z-Data-0.6.1.0-JeXatJjxwtL6zC0T0lLei4" 'False) ((C1 ('MetaCons "Object" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'SourceUnpack 'SourceStrict 'DecidedStrict) (Rec0 (Vector (Text, Value)))) :+: (C1 ('MetaCons "Array" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'SourceUnpack 'SourceStrict 'DecidedStrict) (Rec0 (Vector Value))) :+: C1 ('MetaCons "String" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'SourceUnpack 'SourceStrict 'DecidedStrict) (Rec0 Text)))) :+: (C1 ('MetaCons "Number" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'SourceUnpack 'SourceStrict 'DecidedStrict) (Rec0 Scientific)) :+: (C1 ('MetaCons "Bool" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Bool)) :+: C1 ('MetaCons "Null" 'PrefixI 'False) (U1 :: Type -> Type))))

key :: Functor f => Text -> (Value -> f Value) -> Value -> f Value

Lense for Object element

1. return Null if Value is not an Object or key not exist.
2. Modify will have no effect if Value is not an Object or key not exist.
3. On duplicated keys prefer the last one.

nth :: Functor f => Int -> (Value -> f Value) -> Value -> f Value

Lense for Array element.

1. return Null if Value is not an Array or index not exist.
2. Modify will have no effect if Value is not an Array or index not exist.

parse into JSON Value

parseValue :: Bytes -> (Bytes, Either ParseError Value)

Parse Value without consuming trailing bytes.

parseValue' :: Bytes -> Either ParseError Value

Parse Value, and consume all trailing JSON white spaces, if there're bytes left, parsing will fail.

parseValueChunks :: Monad m => ParseChunks m Bytes ParseError Value

Increamental parse Value without consuming trailing bytes.

Value Parsers

value :: Parser Value

JSON Value parser.

object :: Parser (Vector (Text, Value))

parse json array with leading 123.

array :: Parser (Vector Value)

parse json array with leading 91.

string :: Parser Text

skipSpaces :: Parser ()

The only valid whitespace in a JSON document is space, newline, carriage pure, and tab.

Convert to Scientific

floatToScientific :: Float -> Scientific

Convert IEEE float to scientific notition.

doubleToScientific :: Double -> Scientific

Convert IEEE double to scientific notition.