Why "flat is better than nested"?

[Alex Willmer]

On Oct 25, 2:56 pm, Robin Becker <ro... at reportlab.com> wrote:
> On 25/10/2010 11:07, kj wrote:
>
> > In "The Zen of Python", one of the "maxims" is "flat is better than
> > nested"?  Why?  Can anyone give me a concrete example that illustrates
> > this point?
>
> .......
> I believe that the following illustrates the nesting issue (I think this is from
> somewhere in Chomsky)
>
> The rat ate the corn.
> The rat that the cat killed ate the corn.
> The rat that the cat that the dog chased killed ate the corn.
>
> I believe this is called central embedding.
>
> There's also the old schoolboy saying "I know that that that that that boy said
> is wrong!".
>
> The nested nature makes the semantics quite hard. The same will be true of
> nested tuple/list and similar programming structures.

I agree in the case of a suped-up hierachical record structure that
encourages code like

my_far =
the_record.something.something_else.foo[2].keep_going.bar.baz()

A tree of homogeneous nodes that one walks or recurses into (e.g. a b-
tree or r-tree) is a case where I would ignore this maxim