!in operator?

[Stewart Gordon]

Jason House wrote:
<snip>
> Method 1:
> 
> if (x !in y)
>   foo();
> else{
>   auto z = x in y;
>   bar(z);
> }
> 
> Method 2:
> 
> auto z = x in y;
> if (z is null)
>   foo;
> else
>   bar(z);
> 
> Method 1 essentially calls in twice while method 2 calls in once.
<snip>

But there's no requirement to look it up after finding out whether it's 
there or not.

And how's it any different from

if (x in y) {
     auto z = x in y;
     bar(z);
} else {
     foo();
}

or even

if (x in y) {
     bar(y[x]);
} else {
     foo();
}

?

Besides, why would any decent compiler not optimise it to a single lookup?

Stewart.