!in operator?

[Jason House]

Jeremie Pelletier wrote:

> Why is there no !in operator just like there is a !is operator?
> Is it because this expression evaluates to a pointer to the found element?
> Even so, it would make asserts much easier to write.

That is unfortunately a rather sticky point.  The in operator does not 
return bool.  I think the lack of !in is to encourage writing of efficient 
code.  I'm not really sure though.