56 lines
1.6 KiB
JavaScript
56 lines
1.6 KiB
JavaScript
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import _curry3 from "./internal/_curry3.js";
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/**
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* The `mapAccumRight` function behaves like a combination of map and reduce; it
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* applies a function to each element of a list, passing an accumulating
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* parameter from right to left, and returning a final value of this
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* accumulator together with the new list.
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*
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* Similar to [`mapAccum`](#mapAccum), except moves through the input list from
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* the right to the left.
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*
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* The iterator function receives two arguments, *acc* and *value*, and should
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* return a tuple *[acc, value]*.
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*
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* @func
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* @memberOf R
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* @since v0.10.0
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* @category List
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* @sig ((acc, x) -> (acc, y)) -> acc -> [x] -> (acc, [y])
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* @param {Function} fn The function to be called on every element of the input `list`.
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* @param {*} acc The accumulator value.
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* @param {Array} list The list to iterate over.
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* @return {*} The final, accumulated value.
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* @see R.addIndex, R.mapAccum
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* @example
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*
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* const digits = ['1', '2', '3', '4'];
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* const appender = (a, b) => [b + a, b + a];
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*
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* R.mapAccumRight(appender, 5, digits); //=> ['12345', ['12345', '2345', '345', '45']]
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* @symb R.mapAccumRight(f, a, [b, c, d]) = [
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* f(f(f(a, d)[0], c)[0], b)[0],
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* [
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* f(a, d)[1],
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* f(f(a, d)[0], c)[1],
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* f(f(f(a, d)[0], c)[0], b)[1]
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* ]
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* ]
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*/
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var mapAccumRight =
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/*#__PURE__*/
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_curry3(function mapAccumRight(fn, acc, list) {
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var idx = list.length - 1;
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var result = [];
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var tuple = [acc];
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while (idx >= 0) {
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tuple = fn(tuple[0], list[idx]);
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result[idx] = tuple[1];
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idx -= 1;
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}
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return [tuple[0], result];
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});
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export default mapAccumRight;
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