106 lines
3 KiB
JavaScript
106 lines
3 KiB
JavaScript
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(() => {
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'use strict';
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// REP-CYCLES -------------------------------------------------------------
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// repCycles :: String -> [String]
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const repCycles = xs => {
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const n = xs.length;
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return filter(
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cs => xs === takeCycle(n, cs),
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map(concat, tail(inits(take(quot(n, 2), xs))))
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);
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};
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// cycleReport :: String -> [String]
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const cycleReport = xs => {
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const reps = repCycles(xs);
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return [xs, isNull(reps) ? '(n/a)' : last(reps)];
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};
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// GENERIC ----------------------------------------------------------------
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// compose :: (b -> c) -> (a -> b) -> (a -> c)
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const compose = (f, g) => x => f(g(x));
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// concat :: [[a]] -> [a] | [String] -> String
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const concat = xs => {
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if (xs.length > 0) {
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const unit = typeof xs[0] === 'string' ? '' : [];
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return unit.concat.apply(unit, xs);
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} else return [];
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};
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// cons :: a -> [a] -> [a]
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const cons = (x, xs) => [x].concat(xs);
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// curry :: ((a, b) -> c) -> a -> b -> c
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const curry = f => a => b => f(a, b);
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// filter :: (a -> Bool) -> [a] -> [a]
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const filter = (f, xs) => xs.filter(f);
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// inits :: [a] -> [[a]]
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// inits :: String -> [String]
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const inits = xs => [
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[]
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]
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.concat((typeof xs === 'string' ? xs.split('') : xs)
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.map((_, i, lst) => lst.slice(0, i + 1)));
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// intercalate :: String -> [a] -> String
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const intercalate = (s, xs) => xs.join(s);
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// last :: [a] -> a
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const last = xs => xs.length ? xs.slice(-1)[0] : undefined;
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// map :: (a -> b) -> [a] -> [b]
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const map = (f, xs) => xs.map(f);
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// isNull :: [a] -> Bool
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const isNull = xs => (xs instanceof Array) ? xs.length < 1 : undefined;
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// Integral a => a -> a -> a
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const quot = (n, m) => Math.floor(n / m);
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// replicate :: Int -> a -> [a]
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const replicate = (n, a) => {
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let v = [a],
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o = [];
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if (n < 1) return o;
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while (n > 1) {
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if (n & 1) o = o.concat(v);
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n >>= 1;
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v = v.concat(v);
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}
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return o.concat(v);
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};
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// tail :: [a] -> [a]
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const tail = xs => xs.length ? xs.slice(1) : undefined;
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// take :: Int -> [a] -> [a]
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const take = (n, xs) => xs.slice(0, n);
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// First n members of an infinite cycle of xs
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// takeCycle :: Int -> [a] -> [a]
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const takeCycle = (n, xs) => {
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const lng = xs.length;
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return concat((lng >= n ? xs : replicate(Math.ceil(n / lng), xs)))
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.slice(0, n);
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};
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// unlines :: [String] -> String
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const unlines = xs => xs.join('\n');
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// TEST -------------------------------------------------------------------
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const samples = ["1001110011", "1110111011", "0010010010", "1010101010",
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"1111111111", "0100101101", "0100100", "101", "11", "00", "1"
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];
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return unlines(cons('Longest cycle:\n',
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map(compose(curry(intercalate)(' -> '), cycleReport), samples)));
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})();
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