30 lines
774 B
Lua
30 lines
774 B
Lua
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-- the sieve of of Eratosthenes programmed with coroutines
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-- typical usage: lua -e N=1000 sieve.lua | column
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-- generate all the numbers from 2 to n
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function gen (n)
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return coroutine.wrap(function ()
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for i=2,n do coroutine.yield(i) end
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end)
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end
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-- filter the numbers generated by `g', removing multiples of `p'
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function filter (p, g)
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return coroutine.wrap(function ()
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while 1 do
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local n = g()
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if n == nil then return end
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if math.mod(n, p) ~= 0 then coroutine.yield(n) end
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end
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end)
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end
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N=N or 1000 -- from command line
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x = gen(N) -- generate primes up to N
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while 1 do
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local n = x() -- pick a number until done
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if n == nil then break end
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print(n) -- must be a prime number
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x = filter(n, x) -- now remove its multiples
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end
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