这是一道用集合筛选求质数的题目，程序如下：
const
n=200;
var
s,primes:set of 2..n;
procedure main;
var p,c:2..400;
begin
s:=[2..n];
primes:=[];
p:=2;
c:=2;
repeat
while not (c in s) do p:=p+1;
while not (p in s) do
begin
p:=p+1;
end;
primes:=primes+;
c:=p;
while c