moy-fp/src/Object/lensIndex.js

A functional programming library.

import curry from '../Function/curry'
import nthList from '../List/nthList'
import update from '../List/update'
import lens from './lens'

/**
 * Number -> Lens s a
 * Lens s a = Functor f => (a -> f a) -> s -> f s 
 */
const lensIndex = curry(
  n => lens(nthList(n))(update(n))
)

export default lensIndex