On 2/08/2012, at 5:34 PM, Jonathan Geddes wrote:
Ouch! And that's not even very deeply nested. Imagine 4 or 5 levels deep. It really makes Haskell feel clunky next to `a.b.c.d = val` that you see in other languages.
I was taught that this kind of thing violates the Law of Demeter and that an object should not be mutating the parts of an acquaintance's parts, but should ask the acquaintance to do so. I'd say that a.b.c.d = val is at the very least a sign that some encapsulation did not happen. Semantic editor combinators are ingenious, but they make me feel somewhat uneasy, in that they really are in some sense about the *syntax* (or maybe the concrete representation) of things rather than their *semantics* (or maybe I mean the abstract value).