%//////////////////////////////////////////////////////////
%// Name: Peter M. Maurer
%// Program: Sieve of Eratosthenes
%// Due: Never
%// Language: CLU
%//////////////////////////////////////////////////////////

start_up = proc()
	po: stream := stream$primary_output()
	% define the sieve data structure
	% everything is potentially prime until proven otherwise
	Candidates := fill(0,1001,1)
	% Neither 1 nor 0 is prime, so flag them off
	Candidates[0] := 0
	Candidates[1] := 0
	% start the sieve with the integer 0
	i:int := 0
	while i<1000 do
		% advance to the next un-crossed out number.
		% this number must be a prime
		while i<1000 cand Candidates[i] = 0 do
			i := i + 1
		end
		% insure against running off the end of the data structure
		if i<1000 then
			% cross out all multiples of the prime, starting with 2*p.
			j:int := 2
			while j*i < 1000 do
				Candidates[j*i] := 0
				j := j + 1
			end
			% advance to the next candidate
			i := i + 1
		end
	end
	% all uncrossed-out numbers are prime (and only those numbers)
	% print all primes
	for z:int in int$from_to(0, 999) do
		if Candidates[i] ~= 0 then
         		stream$putl(po, int$unparse(z) || " is prime")
		end
	end
end start_up