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Re: Decorators not worth the effort

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2012/9/14 Chris Angelico <rosuav@gmail.com>:
>
> Trouble is, you're starting with a pretty poor algorithm. It's easy to
> improve on what's poor. Memoization can still help, but I would start
> with a better algorithm, such as:
>
> def fib(n):
>         if n<=1: return 1
>         a,b=1,1
>         for i in range(1,n,2):
>                 a+=b
>                 b+=a
>         return b if n%2 else a
>
> def fib(n,cache=[1,1]):
>         if n<=1: return 1
>         while len(cache)<=n:
>                 cache.append(cache[-1] + cache[-2])
>         return cache[n]
>
> Personally, I don't mind (ab)using default arguments for caching, but
> you could do the same sort of thing with a decorator if you prefer. I
> think the non-decorated non-recursive version is clear and efficient
> though.
>
> ChrisA
> --
> http://mail.python.org/mailman/listinfo/python-list


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'm not saying that with the memoization is the "good" solution, just
that I think it's a very nice example of how to use a decorator, and
maybe a good example to start with a talk on decorators..

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Re: Decorators not worth the effort Jean-Michel Pichavant <jeanmichel@sequans.com> - 2012-09-14 11:28 +0200
  Re: Decorators not worth the effort Duncan Booth <duncan.booth@invalid.invalid> - 2012-09-14 11:26 +0000
    Re: Decorators not worth the effort andrea crotti <andrea.crotti.0@gmail.com> - 2012-09-14 15:12 +0100
    Re: Decorators not worth the effort Chris Angelico <rosuav@gmail.com> - 2012-09-15 00:41 +1000
      Re: Decorators not worth the effort 88888 Dihedral <dihedral88888@googlemail.com> - 2012-09-14 09:37 -0700
      Re: Decorators not worth the effort 88888 Dihedral <dihedral88888@googlemail.com> - 2012-09-14 09:37 -0700
    Re: Decorators not worth the effort andrea crotti <andrea.crotti.0@gmail.com> - 2012-09-14 17:15 +0100
    Re: Decorators not worth the effort Chris Angelico <rosuav@gmail.com> - 2012-09-15 03:30 +1000
      Re: Decorators not worth the effort Neil Cerutti <neilc@norwich.edu> - 2012-09-18 13:19 +0000
        Re: Decorators not worth the effort Chris Angelico <rosuav@gmail.com> - 2012-09-18 23:25 +1000
          Re: Decorators not worth the effort 88888 Dihedral <dihedral88888@googlemail.com> - 2012-09-18 08:14 -0700
          Re: Decorators not worth the effort 88888 Dihedral <dihedral88888@googlemail.com> - 2012-09-18 08:14 -0700
    RE: Decorators not worth the effort "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-09-14 23:14 +0000
  Re: Decorators not worth the effort Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-14 12:01 +0000
    Re: Decorators not worth the effort Tim Chase <python.list@tim.thechases.com> - 2012-09-14 08:06 -0500
      Re: Decorators not worth the effort Steve Howell <showell30@yahoo.com> - 2012-09-14 18:13 -0700
  Re: Decorators not worth the effort Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-09-14 13:49 +0200

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