Re: Problem with sieve.lua test program

[Wim Couwenberg <w.couwenberg@...>]

> I just tried to run the sieve.lua test program (sieve of Eratosthenes 
> via coroutines)
> It runs fine with N=1000 but exits prematurely on larger args. 

Maybe a bit OT but it can be instructive to benchmark sieve.lua 
(performance- and memory-wise) against the even simpler coroutine-less 
version below.

--
Wim


-- the sieve of of Eratosthenes programmed without coroutines
-- typical usage: lua -e N=1000 sieve.lua | column

-- generate all the numbers from 2 to n
function gen (n)
  local i = 1
  return function()
    if i < n then
      i = i + 1
      return i
    end
  end
end

-- filter the numbers generated by `g', removing multiples of `p'
function filter (p, g)
  return function()
    while 1 do
      local n = g()
      if n == nil then return end
      if math.mod(n, p) ~= 0 then return n end
    end
  end
end

N=N or 1000		-- 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