29 lines
736 B
Lua
29 lines
736 B
Lua
-- 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
|