We'll start with a simple Ruby Kata and solve it together, live, with imperative programming.
We'll then fix the many, many, many things we got wrong. Then we'll solve the problem again using patterns from functional programming. You'll leave this talk with a clear and concrete example of why functional programming matters, why immutable code matters, and why it can help you writing bug-free code.
The next time you find yourself writing imperative code, you'll think about... the functional alternative.