Prime numbers with LINQ not working

Question

int limit = 100;
IEnumerable<int> primes = Enumerable.Range(2, limit - 2 + 1);

for (int i = 2; i*i <= limit; i++)
{
    primes = (from item in primes where (item % i != 0) || (item == i) select item);
}

foreach (int prime in primes) Console.WriteLine(prime);

Console.ReadKey();

This is my code to get prime numbers from 2 to 100. Why doesn't it work? Help, please.

You need to capture the local `i` otherwise when you iterate the query it's going to have a value of 11. — juharr, May 12 '18 at 17:54

score 1 · Answer 1 · answered May 12 '18 at 17:56

1

You just need to change it to capture the current value of i.

for (int i = 2; i*i <= limit; i++)
{
    int curr = i;
    primes = (from item in primes 
              where (item % curr != 0) || (item == curr) 
              select item);
}

Otherwise when you iterate the query at the end i will be 11 for all of the comparisons.

answered May 12 '18 at 17:56

juharr

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Oh, so Enumerable.Range is lazy. – SlayerGames44 May 12 '18 at 18:34
Even if `Enumerable.Range` wasn't the Linq query result is. – juharr May 12 '18 at 18:41

Prime numbers with LINQ not working

1 Answers1