53 lines
1.6 KiB
JavaScript
53 lines
1.6 KiB
JavaScript
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import _arity from "./internal/_arity.js";
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import _curry1 from "./internal/_curry1.js";
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import map from "./map.js";
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import max from "./max.js";
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import reduce from "./reduce.js";
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/**
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* Returns a function, `fn`, which encapsulates `if/else, if/else, ...` logic.
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* `R.cond` takes a list of [predicate, transformer] pairs. All of the arguments
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* to `fn` are applied to each of the predicates in turn until one returns a
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* "truthy" value, at which point `fn` returns the result of applying its
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* arguments to the corresponding transformer. If none of the predicates
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* matches, `fn` returns undefined.
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*
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* @func
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* @memberOf R
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* @since v0.6.0
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* @category Logic
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* @sig [[(*... -> Boolean),(*... -> *)]] -> (*... -> *)
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* @param {Array} pairs A list of [predicate, transformer]
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* @return {Function}
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* @see R.ifElse, R.unless, R.when
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* @example
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*
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* const fn = R.cond([
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* [R.equals(0), R.always('water freezes at 0°C')],
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* [R.equals(100), R.always('water boils at 100°C')],
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* [R.T, temp => 'nothing special happens at ' + temp + '°C']
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* ]);
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* fn(0); //=> 'water freezes at 0°C'
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* fn(50); //=> 'nothing special happens at 50°C'
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* fn(100); //=> 'water boils at 100°C'
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*/
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var cond =
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/*#__PURE__*/
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_curry1(function cond(pairs) {
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var arity = reduce(max, 0, map(function (pair) {
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return pair[0].length;
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}, pairs));
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return _arity(arity, function () {
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var idx = 0;
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while (idx < pairs.length) {
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if (pairs[idx][0].apply(this, arguments)) {
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return pairs[idx][1].apply(this, arguments);
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}
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idx += 1;
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}
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});
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});
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export default cond;
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