On Tue, Jul 7, 2009 at 9:48 AM, Derek Parnell<derek@psych.ward> wrote:
> On Tue, 07 Jul 2009 11:01:12 -0500, Andrei Alexandrescu wrote:
>
>> To me they look the same, but if people are happier with wasting vertical space, sure.
>
> I think I've finally worked out why I don't like this syntax. Consider this ...
>
>
>   switch (X) {
>      case 1: funcA(); break;
>      case 2,5,7,10 .. 17, 24, 32: funcB(); break;
>      case 3,6,8,18 .. 23: funcC(); break;
>   }
>
> In other words, allowing a range of value inside a list of values.
>
> How is this possible in today's D?

By adding the word "case" several more times.

I really wish we would just go with two-dots for exclusive, three-dots for inclusive, and make that work consistently everywhere.

The "too similar to see the difference" argument just doesn't hold weight with me.  Unless you're programming in a proportional-width font the difference is pretty obvious.  Or define some other char sequence to mean inclusive range.  Like  a ..|b  or a..:b or a..^b, etc.

--bb

Bill Baxter wrote:
> I really wish we would just go with two-dots for exclusive, three-dots
> for inclusive, and make that work consistently everywhere.
> 
> The "too similar to see the difference" argument just doesn't hold
> weight with me.  Unless you're programming in a proportional-width
> font the difference is pretty obvious.  

That is troublesome because it introduces very weird semantics driven by
counting dots and inserting whitespace. Consider:

int wyda;

void main()
{
    int wyda;
    foreach (i; 0...wyda)
    {
        ....
    }
}

Now there are several problems with this. All of the following compile:

0.....wyda
0....wyda
0... .wyda
0. .. .wyda
0.... wyda
0. ...wyda
0. ....wyda
0.. .wyda

and many others too. Using "..." as a separator in addition to a
trailing symbol is bound to be a complete disaster.

> Or define some other char
> sequence to mean inclusive range.  Like  a ..|b  or a..:b or a..^b,
> etc.

That is more sensible. But as far as switch is concerned, I'm thoroughly
content with what we have now, modulo the 256 limit.


Andrei

Bill Baxter:
>Or define some other char sequence to mean inclusive range.  Like  a ..|b  or a..:b or a..^b, etc.<

The Chapel language uses:
..#
That I think is better than all your alternatives. But I think Andrei doesn't like this too.

Bye,
bearophile

Leandro Lucarella wrote:
> I think the ... operator makes perfect sense because it's more general,
> yo could use array[X...Y] and case X..Y: where appropriate.

and

> doesn't look so bad though, but I think it could be easy to miss the ".."
> when reviewing the code

If it's easy to miss .., then it ought to be really easy to miss the distinction between .. and ... !

bearophile wrote:
> Bill Baxter:
>> Or define some other char sequence to mean inclusive range.  Like  a ..|b  or a..:b or a..^b, etc.<
> 
> The Chapel language uses:
> ..#
> That I think is better than all your alternatives. But I think Andrei doesn't like this too.

I like:

   a .. b+1

to mean inclusive range.

Walter Bright Wrote:
> I like:
>     a .. b+1
> to mean inclusive range.

Me too, but does it work when the upper interval is int.max, char.max, ulong.max, ucent.max, etc?

Bye,
bearophile

Walter Bright, el  7 de julio a las 10:46 me escribiste:
> Leandro Lucarella wrote:
> >I think the ... operator makes perfect sense because it's more general, yo could use array[X...Y] and case X..Y: where appropriate.
> 
> and
> 
> >doesn't look so bad though, but I think it could be easy to miss the ".." when reviewing the code
> 
> If it's easy to miss .., then it ought to be really easy to miss the distinction between .. and ... !

As another people said, use another way to write inclusive range, but keep things consistent =)

-- 
Leandro Lucarella (luca) | Blog colectivo: http://www.mazziblog.com.ar/blog/
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Andrei Alexandrescu wrote:
> Now there are several problems with this. All of the following compile:

Possible solution: treat all sequences as dots as part of the same token, always.

> 0.....wyda
> 0....wyda
> 0.... wyda
> 0... .wyda
> 0.. .wyda
> 0. ....wyda

All rejected by the lexer.

> 0. .. .wyda
> 0. ...wyda

Legal and unambiguous.


-- 
Rainer Deyke - rainerd@eldwood.com

Rainer Deyke wrote:
> Andrei Alexandrescu wrote:
>> Now there are several problems with this. All of the following compile:
> 
> Possible solution: treat all sequences as dots as part of the same
> token, always.
> 
>> 0.....wyda
>> 0....wyda
>> 0.... wyda
>> 0... .wyda
>> 0.. .wyda
>> 0. ....wyda
> 
> All rejected by the lexer.

No. Actually, some, yes :o).

>> 0. .. .wyda
>> 0. ...wyda
> 
> Legal and unambiguous.

And throroughly confusing, which was my point.


Andrei

bearophile wrote:
> Walter Bright Wrote:
>> I like:
>>     a .. b+1
>> to mean inclusive range.
> 
> Me too, but does it work when the upper interval is int.max, char.max, ulong.max, ucent.max, etc?

Nope. Wrap around is always a special case, not just for ranges. It's in the nature of 2's complement arithmetic.