57 lines
2.6 KiB
JavaScript
57 lines
2.6 KiB
JavaScript
import _reduce from "./internal/_reduce.js";
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import _xwrap from "./internal/_xwrap.js";
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import curryN from "./curryN.js";
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/**
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* Initializes a transducer using supplied iterator function. Returns a single
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* item by iterating through the list, successively calling the transformed
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* iterator function and passing it an accumulator value and the current value
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* from the array, and then passing the result to the next call.
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*
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* The iterator function receives two values: *(acc, value)*. It will be
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* wrapped as a transformer to initialize the transducer. A transformer can be
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* passed directly in place of an iterator function. In both cases, iteration
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* may be stopped early with the [`R.reduced`](#reduced) function.
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*
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* A transducer is a function that accepts a transformer and returns a
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* transformer and can be composed directly.
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*
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* A transformer is an an object that provides a 2-arity reducing iterator
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* function, step, 0-arity initial value function, init, and 1-arity result
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* extraction function, result. The step function is used as the iterator
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* function in reduce. The result function is used to convert the final
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* accumulator into the return type and in most cases is
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* [`R.identity`](#identity). The init function can be used to provide an
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* initial accumulator, but is ignored by transduce.
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*
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* The iteration is performed with [`R.reduce`](#reduce) after initializing the transducer.
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*
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* @func
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* @memberOf R
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* @since v0.12.0
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* @category List
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* @sig (c -> c) -> ((a, b) -> a) -> a -> [b] -> a
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* @param {Function} xf The transducer function. Receives a transformer and returns a transformer.
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* @param {Function} fn The iterator function. Receives two values, the accumulator and the
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* current element from the array. Wrapped as transformer, if necessary, and used to
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* initialize the transducer
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* @param {*} acc The initial 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.reduced, R.into
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* @example
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*
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* const numbers = [1, 2, 3, 4];
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* const transducer = R.compose(R.map(R.add(1)), R.take(2));
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* R.transduce(transducer, R.flip(R.append), [], numbers); //=> [2, 3]
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*
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* const isOdd = (x) => x % 2 === 1;
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* const firstOddTransducer = R.compose(R.filter(isOdd), R.take(1));
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* R.transduce(firstOddTransducer, R.flip(R.append), [], R.range(0, 100)); //=> [1]
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*/
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var transduce =
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/*#__PURE__*/
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curryN(4, function transduce(xf, fn, acc, list) {
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return _reduce(xf(typeof fn === 'function' ? _xwrap(fn) : fn), acc, list);
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});
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export default transduce; |