Date: Oct 17, 2012 2:11 PM
Author: kirby urner
Subject: Re: In favor of teaching "dot notation"

On Wed, Oct 17, 2012 at 10:45 AM, Joe Niederberger <
> wrote:

> What's all that got to do with the price of coffee Paul?
> Coffee.price?
> Does coffee in fact have one price or maybe more than one?
> It depends on the context. But we don't really need to talk
> about bananas if we don't care to.
> Joe N

One of the exercises I teach (daily) involves coconut instances, with
different weights. South American, Middle Eastern, and American are our
three coconut types. Some students use subclasses of Coconut and that's a
good solution. Weight may be stored at the class level.


def add_coconut(self, incoming):
if not isinstance(incoming, Coconut):
raise AttributeError("can't add a not-coconut")

That won't come across perfectly unless in plaintext view (a Math Forum
option) but you get the idea: unless the caller of the add_coconut method
is actually passing a coconut object, warning lights go on. It's like TSA
at the airport. If you have a firearm, you really need to be noticed.

Even subclasses of Coconut, like SouthAmerican, make it through. Their
weights are pre-set. But if someone tries to send a different type object
to inventory, the whistle-blowers blow.

"Sensitivity to type" is not stupid. In STEM math, we want students to see
the C > R > Q > Z > N hierarchy. If they don't, they're too illiterate for
STEM. DC has lower standards. Our students tend to be smarter than the
average American, but because of curriculum, not genes. We could assist
the USA, but we aren't required by law to do so (It's "opt in" not "opt