Witchcraft v1.0.0-beta Witchcraft.Functor View Source

Functors are datatypes that allow the application of functions to their interior values. Always returns data in the same structure (same size, tree layout, and so on).

Please note that bitstrings are not functors, as they fail the functor composition constraint. They change the structure of the underlying data, and thus composed lifting does not equal lifing a composed function. If you need to map over a bitstring, convert it to and from a charlist.

Type Class

An instance of Witchcraft.Functor must define Witchcraft.Functor.map/2.

Functor  [map/2]

Link to this section Summary

Functions

<~/2 with arguments flipped

map/2 but with the function automatically curried

map a function into one layer of a data wrapper. There is an autocurrying variant: lift/2

Replace all inner elements with a constant value

Operator alias for lift/2

Link to this section Types

Link to this section Functions

<~/2 with arguments flipped.

iex> (fn x -> x + 5 end) <~ [1,2,3]
[6, 7, 8]

Note that the mnemonic is flipped from |>, and combinging directions can be confusing. It’s generally recommended to use ~>, or to keep <~ on the same line both of it’s arguments:

iex> fn(x, y) -> x + y end <~ [1, 2, 3]
...> |> List.first()
...> |> apply([9])
10

…or in an expression that’s only pointing left:

iex> fn y -> y * 10 end
...> <~ fn x -> x + 55 end
...> <~ [1, 2, 3]
[560, 570, 580]

map/2 but with the function automatically curried

Examples

iex> lift([1, 2, 3], fn x -> x + 1 end)
[2, 3, 4]

iex> [1, 2, 3]
...> |> lift(fn x -> x + 55 end)
...> |> lift(fn y -> y * 10 end)
[560, 570, 580]

iex> [1, 2, 3]
...> |> lift(fn(x, y) -> x + y end)
...> |> List.first()
...> |> apply([9])
10

map a function into one layer of a data wrapper. There is an autocurrying variant: lift/2.

Examples

iex> map([1, 2, 3], fn x -> x + 1 end)
[2, 3, 4]

iex> %{a: 1, b: 2} ~> fn x -> x * 10 end
%{a: 10, b: 20}

iex> map(%{a: 2, b: [1, 2, 3]}, fn
...>   int when is_integer(int) -> int * 100
...>   value -> inspect(value)
...> end)
%{a: 200, b: "[1, 2, 3]"}

Replace all inner elements with a constant value

Examples

iex> replace([1, 2, 3], "hi")
["hi", "hi", "hi"]

Operator alias for lift/2

Example

iex> [1, 2, 3]
...> ~> fn x -> x + 55 end
...> ~> fn y -> y * 10 end
[560, 570, 580]

iex> [1, 2, 3]
...> ~> fn(x, y) -> x + y end
...> |> List.first()
...> |> apply([9])
10