Primality by trial division: Difference between revisions
→Segmented Generate and Test: use function that's already there
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primesST = 2 : 3 : sieve 5 9 (drop 2 primesST) (inits $ tail primesST) where
sieve x q ps (fs:ft) = filter (
++ sieve (q+2) (head ps^2) (tail ps) ft</lang>
<code>inits</code> makes a stream of (progressively growing) prefixes of an input stream, starting with an empty prefix. <code>noDivsBy</code> is [[#Haskell|defined above]].
Runs at empirical <math>O(n^{1.4...})</math> time complexity, in ''n'' primes produced. Can be used as a framework for unbounded segmented sieves, replacing divisibility testing with proper sieve of Eratosthenes on arrays, etc.
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