Why flatten a tree when you can just traverse it?

Michael Feathers wrote a blog post about avoiding explicitly traversing a tree recursively by taking advantage of its representation as nested arrays and using array operations to flatten.

I was unhappy about this solution because

• it creates a bunch of intermediate arrays
• it concatenates arrays repeatedly, which is expensive for a very large tree
• the recursive solution seems more simple, clear, and efficient

So I wrote up the recursive solution. Some features of the solution:

• it uses Ruby’s idiomatic yield construct
• for convenience, it creates an Enumerable so that you can do whatever you want while iterating through the tree

Here’s the code: