'in' for plain arrays?

[Ali Çehreli]

bearophile wrote:
 > Pelle M.:
 >
 >> It doesn't exist for performance reasons, I think.
 >
 > It's not a matter of performance. Walter thinks that "in" on
 > AAs searches on keys. And the "keys" of a dynamic array are its
 > indices. And searching for indices in a dynamic array is not so
 > useful. Therefore no "in" for dynamic/static arrays. I think
 > this line of thought is not practical, and Python gets this
 > better.

I think Walter's is a good point. If 'in' searches among keys for AAs; 
for arrays, it would be implemented trivially as

     (index >= 0) && (index < array_length)

I think that expression allows for negative index values too. And yes, I 
had to check before posting as I can't be sure about the integer 
promotion rules. :)

If 'in' were to search among the values of arrays, then it wouldn't have 
the same meaning with AAs.

Ali