just hit open to start lab and learn ide popped up but does not show that lab has been forked and when I submitted lab via learn submit it is not showing that it has been pushed and lab completed.

remove front matter, add objectives, clarify instructions

http://mathforum.org/library/drmath/view/57036.html

A major part of algo design is thinking about the edge cases. Make sure we have a test that accounts for the weirdness of 0 and 1

Suggest having a solution that's more aligned with what Learners should know at this point in the curriculum. Something like this:

def prime?(n)
  n == 0 || n == 1 ? false : (2..n-1).to_a.all?{|d| n % d != 0}
end

I may be missing something, but it appears prime_spec.rb from the Implementing Prime lab only checks for false returns for 0,1,4,40, and 101013. No negative integers are being tested!

I only came to this conclusion after helping someone else with the lab and noticing they took that specific situation into account. My original code didn't take negatives into account but still passed all tests(It was an easy fix, and I submitted an update).

Others may also have code that passed rspec tests but doesn't truly check for prime numbers!

Figured it might be worth looking at.

Thanks,

-Colby

This might sound like a strange complaint, but it seems like this "Introduction to Enumerators" chapter would have been incredibly useful far earlier in the curriculum, perhaps during the Arrays section. We've been using '.each' fairly extensively already, and to have this incredibly useful definition of what '.each' and '.collect' do right after, say, the "badges" lab seems to be putting the cart before the horse.

2 is the only even prime and is sometimes overlooked. Certain implementations will also start with a base divisor of 3 in order to increment by 2 and skip over even numbers; some students seem to be forgetting about two as a prime.

I also agree with the other open issue; the solution is not only quite confusing, but a somewhat odd and extremely slow implementation of the sieve of eratosthenes that actually ends up being slower than n/2 due to the overhead before it actually calculates. (This could be ameliorated with memoization, or a different implementation, or both.)

Wikipedia still works. Other resource links seem to be dead.