47 lines
1.4 KiB
JavaScript
47 lines
1.4 KiB
JavaScript
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import _curry2 from "./internal/_curry2.js";
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import _dispatchable from "./internal/_dispatchable.js";
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import _makeFlat from "./internal/_makeFlat.js";
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import _xchain from "./internal/_xchain.js";
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import map from "./map.js";
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/**
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* `chain` maps a function over a list and concatenates the results. `chain`
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* is also known as `flatMap` in some libraries.
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*
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* Dispatches to the `chain` method of the second argument, if present,
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* according to the [FantasyLand Chain spec](https://github.com/fantasyland/fantasy-land#chain).
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*
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* If second argument is a function, `chain(f, g)(x)` is equivalent to `f(g(x), x)`.
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*
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* Acts as a transducer if a transformer is given in list position.
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*
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* @func
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* @memberOf R
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* @since v0.3.0
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* @category List
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* @sig Chain m => (a -> m b) -> m a -> m b
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* @param {Function} fn The function to map with
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* @param {Array} list The list to map over
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* @return {Array} The result of flat-mapping `list` with `fn`
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* @example
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*
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* const duplicate = n => [n, n];
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* R.chain(duplicate, [1, 2, 3]); //=> [1, 1, 2, 2, 3, 3]
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*
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* R.chain(R.append, R.head)([1, 2, 3]); //=> [1, 2, 3, 1]
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*/
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var chain =
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/*#__PURE__*/
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_curry2(
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/*#__PURE__*/
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_dispatchable(['fantasy-land/chain', 'chain'], _xchain, function chain(fn, monad) {
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if (typeof monad === 'function') {
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return function (x) {
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return fn(monad(x))(x);
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};
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}
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return _makeFlat(false)(map(fn, monad));
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}));
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export default chain;
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