Repost: make foreach(i, a; range) "just work"

[Regan Heath]

On Thu, 20 Feb 2014 12:56:27 -0000, Marc Schütz <schuetzm at gmx.net> wrote:

> IMO, any change needs to be both backwards-compatible (i.e., it should  
> not only "just work", as you phrased, but existing code should "just  
> keep working"), and forward-compatible, so as not to obstruct any  
> potential improvements of tuple handling.
>
> Scheme #1 fails backwards-compatibility.

Fair enough.  We can always pack things manually using something like the  
enumerate() method mentioned in the link.

> Scheme #2 doesn't, but I feel the matching rules if a type is specified  
> are too complicated. Instead, I would suggest just to always assign the  
> variables from the right, i.e. you cannot skip variables, and if you  
> specify a type, it must match the type of the value in this position.
>
> If you really want to skip a tuple member (in order to avoid an  
> expensive copy), a special token "_" or "$" could be introduced, as has  
> also been suggested in one the tuple unpacking/pattern matching DIPs,  
> IIRC.
>
> As for unpacking a tuple value (or key), an additional pair of  
> parentheses can be used, so such a feature would still be possible in  
> the future:
>
> foreach(i, k, (a,b,c); ...)

Cool.

> (Scheme #3 seems just too complicated for my taste. It's important to be  
> intuitively understandable and predictable.)

Fair enough.

Any comments on the initial solution to my original problem?

R

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