[Tutor] fibonacci

[Gregor Lingl]

Bob Gailer schrieb:

> At 01:24 PM 2/14/2003 +0100, Gregor Lingl wrote:
>
>> def fib1liner(n, f=[0,1]):
>>    return(n+1>len(f))and[(lambda x:f.append(f[-2]+f[-1]))(i)for i in 
>> range(n+1-len(f))]and 0 or f[n]
>
>
> Thanks for a really great example of what can be done using and, or, 
> comprehension. FWIW this can be simplified to:
>
> def fib1liner(n, f=[0,1]):
>    return n>1 and[(lambda:f.append(f[-2]+f[-1]))()for i in 
> range(n-1)]and 0 or f[n]
>
Thanks for you compression - concerning the lambda expression.
However, your oneliner is not exactly eqivalent to the original:
with every call for n > 1 it computes n-1 new fibonacci numbers, while 
the original
version uses the fact, that f - as a mutable object - after every call 
remains changed.
so after you have computed fib1liner(20), f contains all 
fibonacci-numbers up to the 20th.
Every following call with n<20 needs not to compute anything new.
Advantages: (1) no unnecessary computing time
                    (2) no unnecessary memory used

Gregor

P.S. What does FWIW mean?


>
> Bob Gailer
> mailto:ramrom@earthling.net
> 303 442 2625
>
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