71 lines
2.4 KiB
JavaScript
71 lines
2.4 KiB
JavaScript
import _curry3 from "./internal/_curry3.js";
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/**
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* Returns a single item by iterating through the list, successively calling
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* the iterator function and passing it an accumulator value and the current
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* value from the array, and then passing the result to the next call.
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*
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* Similar to [`reduce`](#reduce), except moves through the input list from the
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* right to the left.
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*
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* The iterator function receives two values: *(value, acc)*, while the arguments'
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* order of `reduce`'s iterator function is *(acc, value)*. `reduceRight` may use [`reduced`](#reduced)
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* to short circuit the iteration.
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*
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* Note: `R.reduceRight` does not skip deleted or unassigned indices (sparse
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* arrays), unlike the native `Array.prototype.reduceRight` method. For more details
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* on this behavior, see:
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* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduceRight#Description
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*
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* Be cautious of mutating and returning the accumulator. If you reuse it across
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* invocations, it will continue to accumulate onto the same value. The general
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* recommendation is to always return a new value. If you can't do so for
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* performance reasons, then be sure to reinitialize the accumulator on each
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* invocation.
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*
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* @func
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* @memberOf R
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* @since v0.1.0
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* @category List
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* @sig ((a, b) -> b) -> b -> [a] -> b
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* @param {Function} fn The iterator function. Receives two values, the current element from the array
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* and the accumulator.
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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.reduce, R.addIndex, R.reduced
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* @example
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*
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* R.reduceRight(R.subtract, 0, [1, 2, 3, 4]) // => (1 - (2 - (3 - (4 - 0)))) = -2
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* // - -2
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* // / \ / \
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* // 1 - 1 3
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* // / \ / \
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* // 2 - ==> 2 -1
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* // / \ / \
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* // 3 - 3 4
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* // / \ / \
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* // 4 0 4 0
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*
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* @symb R.reduceRight(f, a, [b, c, d]) = f(b, f(c, f(d, a)))
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*/
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var reduceRight =
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/*#__PURE__*/
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_curry3(function reduceRight(fn, acc, list) {
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var idx = list.length - 1;
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while (idx >= 0) {
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acc = fn(list[idx], acc);
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if (acc && acc['@@transducer/reduced']) {
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acc = acc['@@transducer/value'];
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break;
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}
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idx -= 1;
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}
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return acc;
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});
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export default reduceRight; |