There's a significant difference between a wide understanding of category theory in general and understanding what a monad or a functor is used for in haskell.

There's a significant difference between a wide understanding of category theory in general and understanding what a monad or a functor is used for in haskell. They're just type classes, nothing special. There's not all that much more to know about them besides their definition. I rather disagree that they are undocumented and have no examples. Section 6.3.6 in the haskell report 2010 defines the type class and provides examples: http://www.haskell.org/onlinereport/haskell2010/haskellch6.html#x13-1330006.3.6 http://www.haskell.org/onlinereport/haskell2010/haskellch6.h... See also, the typeclassopedia, which walks through a simple definition, many examples, and discusses general intuition: http://www.haskell.org/haskellwiki/Typeclassopedia#Monad http://www.haskell.org/haskellwiki/Typeclassopedia#Monad Perhaps I've misunderstood you, and maybe you mean that common libraries are undocumented and have no examples? That certainly hasn't been my experience; most libraries I've run into have plenty of documentation for me. Can you give me some examples? Yes, I agree that trying to write haskell without being able to understand simple type classes would be very difficult and confusing, but I disagree with what I understand the implied point to be, perhaps you could clarify this for me? I understand you to be saying here that you expect to be able to proficiently use a language with negligible understanding of how data types work in the language, or the common data types defined in the standard library? That sounds like nonsense to me, so I suspect I'm confused here; can you be a bit more explicit in your criticisms here?