41 lines
1.1 KiB
JavaScript
41 lines
1.1 KiB
JavaScript
(() => {
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'use strict';
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// hofQSeq :: Int -> [Int]
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const hofQSeq = x =>
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x > 2 ? tail(foldl((Q, n) =>
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n < 3 ? Q : Q.concat(
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Q[n - Q[n - 1]] + Q[n - Q[n - 2]]
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), [0, 1, 1],
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range(1, x))) : (x > 0 ? take(x, [1, 1]) : undefined);
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// GENERIC FUNCTIONS -------------------------------------------
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// foldl :: (b -> a -> b) -> b -> [a] -> b
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const foldl = (f, a, xs) => xs.reduce(f, a),
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// range :: Int -> Int -> [Int]
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range = (m, n) =>
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Array.from({
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length: Math.floor(n - m) + 1
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}, (_, i) => m + i),
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// tail :: [a] -> [a]
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tail = xs => xs.length ? xs.slice(1) : undefined,
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// last :: [a] -> a
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last = xs => xs.length ? xs.slice(-1)[0] : undefined,
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// Int -> [a] -> [a]
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take = (n, xs) => xs.slice(0, n);
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// TEST --------------------------------------------------------
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return {
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firstTen: hofQSeq(10),
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thousandth: last(hofQSeq(1000)),
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'Q<Q-1UpTo10E5': hofQSeq(100000)
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.reduce((a, x, i, xs) => x < xs[i - 1] ? a + 1 : a, 0)
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};
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})();
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