Martijn van Steenbergen
1) What's a type of this function? I say *a* type because there are multiple correct answers.
debugWith f = do putStrLn (f True) putStrLn (f 'c')
Don't ask the compiler to infer the type for you; it won't be able to. One of the characteristics of RankNTypes is that the compiler needs you, the programmer, to supply the type.
I randomly guess something like "(forall a. a -> String) -> IO ()" (but haven't done anything myself with existentials so I'm quite possibly wrong).
2) What would be a good argument to debugWith?
Does "show" suffice?
3) What's one reason the compiler can't infer the type for you?
foralls are tricksy little devils? :p -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com