source: node_modules/ramda/es/transduce.js@ d24f17c

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1import _xReduce from "./internal/_xReduce.js";
2import _xwrap from "./internal/_xwrap.js";
3import curryN from "./curryN.js";
4/**
5 * Initializes a transducer using supplied iterator function. Returns a single
6 * item by iterating through the list, successively calling the transformed
7 * iterator function and passing it an accumulator value and the current value
8 * from the array, and then passing the result to the next call.
9 *
10 * The iterator function receives two values: *(acc, value)*. It will be
11 * wrapped as a transformer to initialize the transducer. A transformer can be
12 * passed directly in place of an iterator function. In both cases, iteration
13 * may be stopped early with the [`R.reduced`](#reduced) function.
14 *
15 * A transducer is a function that accepts a transformer and returns a
16 * transformer and can be composed directly.
17 *
18 * A transformer is an object that provides a 2-arity reducing iterator
19 * function, step, 0-arity initial value function, init, and 1-arity result
20 * extraction function, result. The step function is used as the iterator
21 * function in reduce. The result function is used to convert the final
22 * accumulator into the return type and in most cases is
23 * [`R.identity`](#identity). The init function can be used to provide an
24 * initial accumulator, but is ignored by transduce.
25 *
26 * The iteration is performed with [`R.reduce`](#reduce) after initializing the transducer.
27 *
28 * @func
29 * @memberOf R
30 * @since v0.12.0
31 * @category List
32 * @sig (c -> c) -> ((a, b) -> a) -> a -> [b] -> a
33 * @param {Function} xf The transducer function. Receives a transformer and returns a transformer.
34 * @param {Function} fn The iterator function. Receives two values, the accumulator and the
35 * current element from the array. Wrapped as transformer, if necessary, and used to
36 * initialize the transducer
37 * @param {*} acc The initial accumulator value.
38 * @param {Array} list The list to iterate over.
39 * @return {*} The final, accumulated value.
40 * @see R.reduce, R.reduced, R.into
41 * @example
42 *
43 * const numbers = [1, 2, 3, 4];
44 * const transducer = R.compose(R.map(R.add(1)), R.take(2));
45 * R.transduce(transducer, R.flip(R.append), [], numbers); //=> [2, 3]
46 *
47 * const isOdd = (x) => x % 2 !== 0;
48 * const firstOddTransducer = R.compose(R.filter(isOdd), R.take(1));
49 * R.transduce(firstOddTransducer, R.flip(R.append), [], R.range(0, 100)); //=> [1]
50 */
51
52var transduce =
53/*#__PURE__*/
54curryN(4, function transduce(xf, fn, acc, list) {
55 return _xReduce(xf(typeof fn === 'function' ? _xwrap(fn) : fn), acc, list);
56});
57export default transduce;
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