4/6/15 - Permutations in Ruby

I rewrote my ruby permutations algorithm to use yield instead of return. This is a lazy algorithm: rather than generating all permutations at once, it generates them as they are needed. So the line permutations(%w[a b c d]).first(5) only generates the first 5 permutations of the array. Here is the implementation: As it turns out, this function is already built into ruby! This statement does the exact same thing.