Incredibly slow with large value arrays - this method for finding primes takes forever. If anyone sees this, this is very bad practice. He's doing n-complexity calls multiple times in each loop. I'd have to totally deconstruct his solution to guess at the complexity - but it's bad.

Insanely slow if you have very large strings - clever but very, very slow. For example, running this "("*100000 + ")"*100000 takes 30 seconds, another magnitude and you're looking at hours. This is due to n calls of replace within the loop making this this algorithm O(n^2).

Repeatedly converts value to str in loop and calculates the link - better to sacrifice the one-liner and store the conversions in variables outside teh generator.