[Haskell-cafe] Re: Are there standard idioms for lazy, pure error handling?

Nicolas Pouillard wrote:

Henning Thielemann wrote:

...

@Apfelmus:

For practical purposes I think Train should have swapped type parameters in order to make Functor act on the type of the list elements.

data Train b a = Wagon a (Train b a) | Loco b

The functor on the Loco/Caboose makes sense too and swapping the arguments is less natural to read.

It's a bifunctor! :D I don't really mind. The application "list that may end with an error" uses a fixed b , so putting the a at the end makes sense. Regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com