My body was clearly not ready to do regex research again. I was adding in slashes like I was in a horror flick until I finally just tried putting the darn i where it belonged

ah! of course! Thankyou! Quite elegant, actually!

why don't you have to include "self" before the methods?

case insensitive regex.
it will match both upper and lowercase vowels.

Yeah, @muyifeng1988. This solution have a lot of bugs :)

I agree with the other comments here, so I have no criticisms to add. Solutions like this make me want to delve even further into ruby. This answer is very elegant and makes me want to focus more on trying to create one line solutions.

This way you ensure the string spans from beginning to the end with just one letter. Otherwise you would match any string with a vowel, for example 'codewars'. Because of the above, your solution wouldn't work with the current test set.

This is correct the above solution would fail with an empty array. Although I think returning nil on an empty array instead of NaN is satisfactory.

wut

Lame...how is shit like this even out of beta

@serjmil: Please mark solution related comments as spoilers.

I think sum and average can be better, (BTW, other methods are excellent!)

def sum
reduce(0, :+)
end

def average
empty? ? NaN : sum / size # As description says average() on an empty array must return NaN
end

This solution is not good enough. If there is an empty array, sum method will return nil, i think it's better to return 0. Also average method will lead to error if size is 0.

[].reduce(:+) => nil

0 / 0 => error