31 lines
647 B
JavaScript
31 lines
647 B
JavaScript
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(function () {
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// [a] -> [[a]]
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function permutations(xs) {
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return xs.length ? (
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chain( xs, function (x) {
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return chain( permutations(deleted(x, xs)), function (ys) {
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return ( [[x].concat(ys)] );
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})})) : [[]]
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}
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// monadic bind/chain for lists
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function chain(xs, f) {
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return [].concat.apply([], xs.map(f));
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}
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// drops first instance found
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function deleted(x, xs) {
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return xs.length ? (
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x === xs[0] ? xs.slice(1) : [xs[0]].concat(
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deleted(x, xs.slice(1))
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)
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) : [];
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}
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return permutations(['Aardvarks', 'eat', 'ants'])
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})();
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