Consecutive primes with ascending or descending differences: Difference between revisions
Consecutive primes with ascending or descending differences (view source)
Revision as of 09:49, 2 November 2021
, 2 years ago→{{header|Haskell}}: Removed a typo (trailing W prevented compilation after `primes`) added explicit module import
(→{{header|Haskell}}: added solution) |
m (→{{header|Haskell}}: Removed a typo (trailing W prevented compilation after `primes`) added explicit module import) |
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=={{header|Haskell}}==
Uses prime generator implemented in the [[Sieve_of_Eratosthenes#Improved_efficiency_Wheels]].
<lang haskell>import Data.Numbers.Primes
<lang haskell>-- generates consecutive subsequences defined by given equivalence relation▼
consecutives equiv = filter ((> 1) . length) . go []
where
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go (y:ys) (h:t) | y `equiv` h = go (h:y:ys) t
| otherwise = (y:ys) : go [h] t
-- finds maximal values in a list and returns the first one
maximumBy g (h:t) = foldr f h t
where f r x = if g r < g x then x else r
-- the task implementation
task ord n = reverse $ p+s : p : (fst <$> rest)
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$ consecutives (\(_,a) (_,b) -> a `ord` b)
$ differences
$ takeWhile (< n)
differences l = zip l $ zipWith (-) (tail l) l</lang>
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