Functional programming provides programmers with a powerful set of techniques. Over the last few years, many programmers have brought these ideas into their work, in a variety of languages. But functional programming, like all programming techniques, isn’t a perfect solution to all problems. In this talk, Rúnar Bjarnason shows us where some of the problems are with functional programming, and where (and why) the tradeoffs are still useful. His examples are in Scala, but the examples are applicable to many functional languages.