input validation

[bearophile]

Andrei Alexandrescu:
> Binary search is rather common.

Oh, yes, sorry, I meant among the ones you have listed there...


> As an aside, your use of "index" suggests you return integrals out of 
> the function. IMHO that's strongly unrecommended.

I don't want to use too much of your time (that it may be better spent with your new child), but I don't understand what you mean.
That index() function is meant the index position of the item or sub-sequence into the bigger array (or iterable), and it returns -1 if not found. This is an usual design.
Some people think that such controls for -1 value aren't always done, so to avoid that and some bugs, it's better to raise something like IndexException when the needle isn't found.

Bye,
bearophile