Runar Bjarnason has been exploring how writing in a functional style increases modularity and compositionality of software for many years. He is co-author of functional programming in scala, a book that teaches these principles in scala.

In this interview with Runar explains how writing in a functional style  involves limiting side effects, avoiding exceptions and using higher order abstractions.  Writing in this style places constraints on what a module in a software system may do, but by constraining modules in this may, the software modules themselves become endlessly composable.  

Show Notes:

Functional Programming In Scala

Constraints Liberate