Needless copying in iterations?

[Marc 'BlackJack' Rintsch]

On Sat, 15 Sep 2007 14:58:15 -0700, James Stroud wrote:

> I was staring at a segment of code that looked like this today:
> 
>     for something in stuff[x:y]:
>       whatever(something)
> 
> and was wondering if the compiler really made a copy of the slice from 
> stuff as the code seems to suggest, or does it find some way to produce 
> an iterator without the need to make a copy (if stuff is a built-in 
> sequence type)?

The compiler can't "optimize" this as it would change the semantics. 
There's no way for the compiler to tell if this copy really is "needless".
`whatever()` may change `stuff[i]` where `i` is in `x:y` and this may lead
to different results wether it iterates over a copy or the original.

Ciao,
	Marc 'BlackJack' Rintsch