Calculating monad transformers with category theory

by oleksandrmanzyuk

I have noticed recently that the the standard monad transformers — state, reader, writer, error – can be interpreted as instances of one general categorical construction: translation of a monad along an adjunction. I have taken time to write down what exactly I mean by this. The result is this note. I consider it an elaboration of Derek Elkins’ “Calculating monads with category theory” (The Monad.Reader Issue 13), hence the title. If you like the note (and even if you don’t), I’d be glad to hear from you.