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diff --git a/tests/Smoke/sieve.lua b/tests/Smoke/sieve.lua
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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