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- -- sieve.lua
- -- the sieve of Eratosthenes programmed with coroutines
- -- typical usage: lua -e N=500 sieve.lua | column
- -- generate all the numbers from 2 to n
- function gen (n)
- return coroutine.wrap(function ()
- for i=2,n do coroutine.yield(i) end
- end)
- end
- -- filter the numbers generated by `g', removing multiples of `p'
- function filter (p, g)
- return coroutine.wrap(function ()
- for n in g do
- if n%p ~= 0 then coroutine.yield(n) end
- end
- end)
- end
- N=N or 500 -- from command line
- x = gen(N) -- generate primes up to N
- while 1 do
- local n = x() -- pick a number until done
- if n == nil then break end
- print(n) -- must be a prime number
- x = filter(n, x) -- now remove its multiples
- end
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