Optional parameters referring to previous parameters?

[Mehrdad]

On Thursday, 10 May 2012 at 11:54:42 UTC, Steven Schveighoffer 
wrote:
> I *love* this idea.

:D

> Although, what happens if the expression for items is costly?  
> We have to make sure if you do:
>
> process(someExpensiveCalculation());
>
> it doesn't turn into:
>
> process(someExpensiveCalculation(), 
> someExpensiveCalculation().length);

It should be evaluated once anyway, since it might have side 
effects.