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x/ramda/scan.js

:ram: Practical functional Javascript
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import _curry3 from './internal/_curry3';

/** * Scan is similar to [`reduce`](#reduce), but returns a list of successively * reduced values from the left * * @func * @memberOf R * @since v0.10.0 * @category List * @sig ((a, b) -> a) -> a -> [b] -> [a] * @param {Function} fn The iterator function. Receives two values, the accumulator and the * current element from the array * @param {*} acc The accumulator value. * @param {Array} list The list to iterate over. * @return {Array} A list of all intermediately reduced values. * @see R.reduce, R.mapAccum * @example * * const numbers = [1, 2, 3, 4]; * const factorials = R.scan(R.multiply, 1, numbers); //=> [1, 1, 2, 6, 24] * @symb R.scan(f, a, [b, c]) = [a, f(a, b), f(f(a, b), c)] */var scan = _curry3(function scan(fn, acc, list) { var idx = 0; var len = list.length; var result = [acc]; while (idx < len) { acc = fn(acc, list[idx]); result[idx + 1] = acc; idx += 1; } return result;});export default scan;