Concatenate two primes is also prime: Difference between revisions
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(→{{header|Ruby}}: Add Ruby) |
(→{{header|ALGOL 68}}: Use ALGOL 68-primes) |
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INT max prime = max low prime * max low prime; |
INT max prime = max low prime * max low prime; |
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# sieve the primes to max prime # |
# sieve the primes to max prime # |
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PR read "primes.incl.a68" PR |
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[ 1 : max prime ]BOOL prime; |
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[]BOOL prime = PRIMESIEVE max prime; |
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FOR i FROM 3 BY 2 TO UPB prime DO prime[ i ] := TRUE OD; |
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FOR i FROM 4 BY 2 TO UPB prime DO prime[ i ] := FALSE OD; |
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FOR i FROM 3 BY 2 TO ENTIER sqrt( UPB prime ) DO |
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IF prime[ i ] THEN FOR s FROM i * i BY i + i TO UPB prime DO prime[ s ] := FALSE OD FI |
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OD; |
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# construct a list of the primes up to the maximum low prime to consider # |
# construct a list of the primes up to the maximum low prime to consider # |
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[ 1 : max low prime ]INT low prime; |
[ 1 : max low prime ]INT low prime; |