Decorators not worth the effort

[Joshua Landau]

On 14 September 2012 18:30, Chris Angelico <rosuav at gmail.com> wrote:

> On Sat, Sep 15, 2012 at 2:15 AM, andrea crotti
> <andrea.crotti.0 at gmail.com> wrote:
> > The poor algorithm is much more close to the mathematical definition
> > than the smarter iterative one..  And in your second version you
> > include some ugly caching logic inside it, so why not using a
> > decorator then?
>
> I learned Fibonacci as a sequence, not as a recursive definition. So
> the algorithm I coded (the non-caching one) is pretty much how I
> learned it in mathematics. But yes, you're right that the caching is
> inherent to the second version; and yes, that's where a decorator can
> make it a LOT cleaner.
>
> As a demo of recursion and decorators, your original function pair is
> definitely the best. But if you want to be able to calculate fib(n)
> for any n without blowing your stack, my version will scale much more
> safely.
>
> But then again, who actually ever needs fibonacci numbers?
>

I thought the example was good, not because  a recursive fib is useful but
because memoizing is. There are a lot of times one would like to memoize
a function: not just recursive ones. Thus, the example of the decorator was
valid.

[offtopic]
Anyhow, the "best" method has to be this:

>>> from decimal import Decimal as Dec
>>> def fib(n):
...     rootFive = Dec(5).sqrt()
...     phi = (1 + rootFive) / 2
...     return round(phi**n / rootFive)
>>> fib(100)
354224848179261915075

It's just so obvious why it works.
[/offtopic]
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