[plt-scheme] macro question

Matthias Felleisen wrote:

>> How do contracts fit into this view?
> 
> I am giving two answers because I am not sure what the question aims at:

Thanks, Matthias. My question was aiming on the technical side, but the 
pedagogical side is also intriguing. Understanding the error messages 
that result when HM-style type inference fails (at least in my limited 
experience with SML and GHC) seems to me to be the largest barrier to 
moving freshmen or sophomores from HtDP into a statically-typed 
environment with a sensible type system. --PR