Optics ​

For a comprehensive understanding of the optics concept, you can refer to arxiv 2001.07488v3.

Lens ​

Optical components for focusing on specific parts of data structures.

Lens.of() ​

Constructs a lens.

• Type

• Details

The first argument is a getter function, and the second argument is a setter function. The function returns a lens that can be used to get, set, or modify a specific part of a data structure.

• Example

Lens.of((s) => s.a, assoc('a'));

Lens.of((s) => s.a, assoc('a'));

Lens.bind() ​

Binds an element directly to a lens.

• Type

Overload 1 ​

Overload 2 ​

• Details

Creates a lens that focuses on the specified element or path within a data structure.

• Example

Lens.bind('a');
Lens.bind(['a', 'b']);

Lens.bind('a');
Lens.bind(['a', 'b']);

view ​

Returns the part of a data structure that a lens is focused on.

• Type

• Details

Takes a lens and a data structure as arguments and returns the part of the data structure that the lens is focused on.

• Example

const lens = Lens.bind('a');
view(lens, { a: 1 }); // 1

const lens = Lens.bind('a');
view(lens, { a: 1 }); // 1

set ​

Sets the value of the part of a data structure that a lens is focused on.

• Type

• Details

Takes a lens, a value to set, and a data structure as arguments. It returns a new data structure with the value set at the focus of the lens.

• Example

const lens = Lens.bind('a');
set(lens, 2, { a: 1 }); // { a: 2 }

const lens = Lens.bind('a');
set(lens, 2, { a: 1 }); // { a: 2 }

over ​

Applies a function to the part of a data structure that a lens is focused on.

• Type

• Details

Takes a lens, a function to apply, and a data structure as arguments. It returns a new data structure where the function has been applied to the focus of the lens.

• Example

const lens = Lens.bind('a');
over(lens, add(1), { a: 1 }); // { a: 2 }

const lens = Lens.bind('a');
over(lens, add(1), { a: 1 }); // { a: 2 }