Processors are used for doing various tasks, usually not limited in usefulness to one particular view function.

• View processors

These take a view function and return a view function. Alternatively, take a view function and a request and return an IO (Maybe Response). This allows them to do both request pre-processing and response post-processing. They will be usually be used as 'decorators' when defining routes.

• View functions

These are straightforward view functions which happen to work as a kind of pre-handler. They are installed using routes, usually before all the others. These usually do redirects, for example addSlashRedirectView

• Response processors

These take a response and the original request object, and return a possibly modified response. This can be useful for post-processing, or adding headers etc.