Summarize primes: Difference between revisions
Content added Content deleted
(→{{header|ALGOL 68}}: Small change so it can also do the "Prime numbers p which sum of prime numbers less or equal to p is prime" task) |
m (Forth - faster without using a sieve) |
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=={{header|Forth}}== |
=={{header|Forth}}== |
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{{works with|Gforth}} |
{{works with|Gforth}} |
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<lang forth>: prime? ( n -- |
<lang forth>: prime? ( n -- flag ) |
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dup 2 < if drop false exit then |
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: notprime! ( n -- ) here + 1 swap c! ; |
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dup 2 mod 0= if 2 = exit then |
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dup 3 mod 0= if 3 = exit then |
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: prime_sieve { n -- } |
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here n erase |
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0 notprime! |
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1 notprime! |
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n 4 do i notprime! 2 +loop |
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then |
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begin |
begin |
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2dup dup * >= |
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while |
while |
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2dup mod 0= if 2drop false exit then |
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dup prime? if |
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n over dup * do |
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i notprime! |
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dup 2* +loop |
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then |
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2 + |
2 + |
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2dup mod 0= if 2drop false exit then |
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repeat |
repeat |
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2drop true ; |
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: main |
: main |
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0 0 { count sum } |
0 0 { count sum } |
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." count prime sum" cr |
." count prime sum" cr |
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100000 prime_sieve |
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1000 2 do |
1000 2 do |
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i prime? if |
i prime? if |
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