jiapengyu
51 lines
1.6 KiB
JavaScript
51 lines
1.6 KiB
JavaScript
import _curry3 from './internal/_curry3';
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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, *value* and *acc*, and should
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* return a tuple *[value, acc]*.
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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 ((x, acc) -> (y, acc)) -> acc -> [x] -> ([y], acc)
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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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* var digits = ['1', '2', '3', '4'];
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* var append = (a, b) => [a + b, a + b];
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*
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* R.mapAccumRight(append, 5, digits); //=> [['12345', '2345', '345', '45'], '12345']
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* @symb R.mapAccumRight(f, a, [b, c, d]) = [
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* [
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* f(b, f(c, f(d, a)[0])[0])[1],
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* f(c, f(d, a)[0])[1],
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* f(d, a)[1],
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* ]
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* f(b, f(c, f(d, a)[0])[0])[0],
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* ]
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*/
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var mapAccumRight = /*#__PURE__*/_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(list[idx], tuple[0]);
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result[idx] = tuple[1];
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idx -= 1;
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}
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return [result, tuple[0]];
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});
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export default mapAccumRight; |