Discarding multiples of 2 and 3 , we only have to look up for primes in 6i + 1 and 6i + 5, or starting an interation from 5 , 6i and 6i + 2 (i and i +2, step by 6). Meaning we would only look up numbers like 5, 7, 11, 13, 17, 19, 23, 25 (see, some of them would still not be prime).

Overall this reduce the iteration to a third.

So if we loop from 5 (having covered previous cases), we check x % i == 0 and x % i + 2 == 0 and i+=6 each loop, we save a lot of time for big numbers.

If some of you are interested, discarding multiples of 2 and 3 (i think), we only have to look up for primes in 6i + 1 and 6i + 5, or starting an interation from 5 , 6i and 6i + 2 (i and i +2, step by 6). Meaning we would only look up numbers like 5, 7, 11, 13, 17, 19, 23, 25 (see, some of them would still not be prime).

Overall this reduce the iteration to a third.

If some of you are interested, discarding multiples of 2 and 3 (i think), we only have to look up for primes in 6i + 1 and 6i + 5, or starting an interation from 5 , 6i and 6i + 2 (i and i +2, step by 6). Meaning we would only look up numbers like 5, 7, 11, 13, 17, 19, 23, 25 (see, some of them would still not be prime).

Overall this reduce the iteration to a third.

you literally can just assign a value to a variable in each case and then use it in the mega block that you are repeating over and over

the f..?

If we initialize sum as 0, can't we skip first lenght check? 'for' wouldn't iterate through an empty array so sum would still be 0 and would be returned without any problem. Also .iter() is not necessary I think

More readable than other one-line options thank you very much ^^

As a rust beginner, are we suposed to code like that always?... 😨