Data.Yaml.YamlLight.Lens

Lenses for working with YAML structures.

Traversals

nth :: Int -> Traversal' YamlLight YamlLight

Lens into a sequence.

>>> YSeq [YStr "a", YStr "b", YStr "c"] ^? nth 1
Just (YStr "b")

>>> YSeq [YStr "a", YStr "b", YStr "c"] & nth 1 .~ YStr "B"
YSeq [YStr "a",YStr "B",YStr "c"]

>>> YSeq [YStr "a", YStr "b", YStr "c"] ^? nth 2 . _Yaml :: Maybe String
Just "c"

key :: ByteString -> Traversal' YamlLight YamlLight

Lens into a mapping. ByteStrings are used as keys directly. If you wish to use a complex mapping key, see key'.

>>> let m = YMap $ Map.fromList [(YStr "name", YStr "Tony Stark"), (YStr "sequels", YStr "2")]
>>> m & key "sequels" . _Yaml +~ 1
YMap (fromList [(YStr "name",YStr "Tony Stark"),(YStr "sequels",YStr "3")])

key' :: YamlLight -> Traversal' YamlLight YamlLight

Lens into a mapping using a complex key.

Yaml parsing prism

_Yaml :: AsYaml a => Prism' YamlLight a

Convert between YAML values and corresponding common Haskell values.

>>> YStr "-2.3" ^? _Yaml :: Maybe Double
Just (-2.3)

>>> YStr "7b.3" ^? _Yaml :: Maybe Double
Nothing

>>> YStr "-23" ^? _Yaml :: Maybe Int
Just (-23)

>>> YStr "Help, I'm trapped in a haddock factory!" ^? _Yaml :: Maybe String
Just "Help, I'm trapped in a haddock factory!"

>>> YStr "An integer" ^? _Yaml :: Maybe Integer
Nothing

If we just want to pull out those values that were successfully parsed,

>>> let nums = YSeq [YStr "3", YStr "2a", YStr "1"]
>>> nums ^.. each._Yaml :: [Int]
[3,1]

Alternately, we may want to fail the entire parse if any element fails to parse.

>>> sequenceA $ map (preview _Yaml) (nums ^.. each) :: Maybe [Int]
Nothing
>>> let nums' = YSeq [YStr "3", YStr "2", YStr "1"]
>>> sequenceA $ map (preview _Yaml) (nums' ^.. each) :: Maybe [Int]
Just [3,2,1]

class AsYaml a where

Convert between YAML values and common types of Haskell values.

Minimal complete definition

fromYaml, toYaml

Methods

fromYaml :: YamlLight -> Maybe a

toYaml :: a -> YamlLight

Instances

AsYaml Bool

Defined in Data.Yaml.YamlLight.Lens

Methods

fromYaml :: YamlLight -> Maybe Bool

toYaml :: Bool -> YamlLight

AsYaml Double

Defined in Data.Yaml.YamlLight.Lens

Methods

fromYaml :: YamlLight -> Maybe Double

toYaml :: Double -> YamlLight

AsYaml Int

Defined in Data.Yaml.YamlLight.Lens

Methods

fromYaml :: YamlLight -> Maybe Int

toYaml :: Int -> YamlLight

AsYaml Integer

Defined in Data.Yaml.YamlLight.Lens

Methods

fromYaml :: YamlLight -> Maybe Integer

toYaml :: Integer -> YamlLight

AsYaml String

Defined in Data.Yaml.YamlLight.Lens

Methods

fromYaml :: YamlLight -> Maybe String

toYaml :: String -> YamlLight

AsYaml ByteString

Defined in Data.Yaml.YamlLight.Lens

Methods

fromYaml :: YamlLight -> Maybe ByteString

toYaml :: ByteString -> YamlLight

AsYaml [YamlLight]

Defined in Data.Yaml.YamlLight.Lens

Methods

fromYaml :: YamlLight -> Maybe [YamlLight]

toYaml :: [YamlLight] -> YamlLight

AsYaml (Map YamlLight YamlLight)

Defined in Data.Yaml.YamlLight.Lens

Methods

fromYaml :: YamlLight -> Maybe (Map YamlLight YamlLight)

toYaml :: Map YamlLight YamlLight -> YamlLight

Numeric parsers

yamlInt :: Integral b => YamlLight -> Maybe b

Try to parse an Integral value from a YamlLight.

yamlReal :: Fractional b => YamlLight -> Maybe b

Try to parse a Fractional value from a YamlLight.

Orphan instances

Ixed YamlLight

Methods

ix :: Index YamlLight -> Traversal' YamlLight (IxValue YamlLight)

At YamlLight

Methods

at :: Index YamlLight -> Lens' YamlLight (Maybe (IxValue YamlLight))

Plated YamlLight

Methods

plate :: Traversal' YamlLight YamlLight

Each YamlLight YamlLight YamlLight YamlLight

Methods

each :: Traversal YamlLight YamlLight YamlLight YamlLight