In my PhD thesis, I worked on integrating contextual information into a type system of functional programming languages. For example, say your mobile application accesses something from the environment such as GPS sensor or your Facebook friends. With coeffects, this could be a part of the type. Rather than having type string -> Person, the type of a function would also include resources and would be string -{ gps, fb }-> Person. I wrote longer introduction to coeffects on this blog before. As one might ex[...]