Toml.Codec.Combinator.List

TOML-specific combinators for converting between TOML and Haskell list-like data types.

There are two way to represent list-like structures with the tomland library.

• Ordinary array lists of primitives:

  foo = [100, 200, 300]
  

• Lists via tables:

  foo =
      [ {x = 100}
      , {x = 200}
      , {x = 300}
      ]
  
  OR
  
  [[foo]]
      x = 100
  [[foo]]
      x = 200
  [[foo]]
      x = 300
  

You can find both types of the codecs in this module for different list-like structures. See the following table for the better understanding:

Haskell Type	TOML	TomlCodec
[Int]	a = [1, 2, 3]	arrayOf _Int "a"
NonEmpty Int	a = [11, 42]	arrayNonEmptyOf _Int "a"
[Text]	x = [{a = "foo"}, {a = "bar"}]	list (text "a") "x"
NonEmpty Text	x = [{a = "foo"}, {a = "bar"}]	nonEmpty (text "a") "x"

Since: 1.3.0.0

Array lists

arrayOf :: TomlBiMap a AnyValue -> Key -> TomlCodec [a]

Codec for list of values. Takes converter for single value and returns a list of values.

Example:

Haskell [Int] can look like this in your TOML file:

foo = [1, 2, 3]

If the key is not present in TOML the following decode error will be spotted:

tomland decode error:  Key foo is not found

Since: 0.1.0

arrayNonEmptyOf :: TomlBiMap a AnyValue -> Key -> TomlCodec (NonEmpty a)

Codec for non- empty lists of values. Takes converter for single value and returns a non-empty list of values.

Example:

Haskell NonEmpty Int can look like this in your TOML file:

foo = [1, 2, 3]

If you try to decode an empty TOML list you will see the error:

tomland decode error:  Empty array list, but expected NonEmpty

If the key is not present in TOML the following decode error will be spotted:

tomland decode error:  Key foo is not found

Since: 0.5.0

Table lists

list :: forall a. TomlCodec a -> Key -> TomlCodec [a]

Codec for list of values. Represented in TOML as array of tables.

Example:

Haskell [Int] can look like this in your TOML file:

foo =
  [ {a = 1}
  , {a = 2}
  , {a = 3}
  ]

Decodes to an empty list [] when the key is not present.

Since: 1.0.0

nonEmpty :: forall a. TomlCodec a -> Key -> TomlCodec (NonEmpty a)

Codec for NonEmpty list of values. Represented in TOML as array of tables.

Example:

Haskell NonEmpty Int can look like this in your TOML file:

foo =
  [ {a = 1}
  , {a = 2}
  , {a = 3}
  ]

If you try to decode an empty TOML list you will see the error:

tomland decode error:  Table array [[foo]] is not found

or

tomland decode error:  Key foo.a is not found

If the key is not present in TOML the following decode error will be spotted:

tomland decode error:  Table array [[foo]] is not found

Since: 1.0.0