Wed May 22 15:47:50 EDT 2019

code is a detail

Obvious in retrospect, but a powerful type system really brings that
point home.  The only thing that matters are the relations between
data types, which are visible in a function's signatures.

What's inside the function is just the nitty gritty details about how
exactly we bridge the high level abstraction (the type sigature) with
machine code that changes one into the other.