lensIndex.js•779 B
var _curry1 = require('./internal/_curry1');
var lens = require('./lens');
var nth = require('./nth');
var update = require('./update');
/**
* Returns a lens whose focus is the specified index.
*
* @func
* @memberOf R
* @since v0.14.0
* @category Object
* @typedefn Lens s a = Functor f => (a -> f a) -> s -> f s
* @sig Number -> Lens s a
* @param {Number} n
* @return {Lens}
* @see R.view, R.set, R.over
* @example
*
* var headLens = R.lensIndex(0);
*
* R.view(headLens, ['a', 'b', 'c']); //=> 'a'
* R.set(headLens, 'x', ['a', 'b', 'c']); //=> ['x', 'b', 'c']
* R.over(headLens, R.toUpper, ['a', 'b', 'c']); //=> ['A', 'b', 'c']
*/
module.exports = _curry1(function lensIndex(n) {
return lens(nth(n), update(n));
});