Effectful Traversals

In this chapter, we are going to bring our treatment of the higher-kinded interfaces in the Prelude to an end. In order to do so, we will continue developing the CSV reader we started implementing in chapter Functor and Friends. I moved some of the data types and interfaces from that chapter to their own modules, so we can import them here without the need to start from scratch.

Note that unlike in our original CSV reader, we will use Validated instead of Either for handling exceptions, since this will allow us to accumulate all errors when reading a CSV file.