Template class with dispatched properties

[Ross Hays]

On Friday, 8 November 2013 at 04:28:31 UTC, Ross Hays wrote:
>> Strange. I'm getting a different error, but I'm still running 
>> 2.063.2.
>> The error I get is
>> `Error: cannot resolve type for t.opDispatch!("x")`
>> What version are you running?
>
> I just updated to 2.064.2
>
>> In any case, the reason apparently is multifold:
>> 1. Apparently the proper error message isn't shown when using 
>> the property notation. (I'd have to check to see if it happens 
>> in 2.064 ... might be a fixed bug)
>> 2. `.charAt(0)` doesn't exist for D's strings. You can just 
>> use bracket notation to access the index.
>> 3. When args is empty (as it will be for a getter, when you 
>> call) args[0] doesn't exist, so `Error: array index [0] is 
>> outside array bounds [0 .. 0]`
>>
>> So fix 2 and 3 and it works for getting x. The reason I use a 
>> static if is to separate the cases where args has items and 
>> when it does not (since args[0] is invalid when args.length == 
>> 0), so that'll be necessary to get it to work.
>
> Okay 2 is fixed, leftovers of other languages in my mind.
> Also took care of 3 I think but I may still be missing 
> something.
>
> Here is what I have now..
>
>
> class Vector(int N, T) if (N <= 3) {
>     T[N] data;
>
>     this()
>     {
>     	data[] = 0;
>     }
>
>     @property ref T opDispatch(string fieldName, Args ...)(Args 
> args)
>         if (Args.length < 2 && fieldName.length == 1 && 
> toOffset(fieldName) < N)
>     {
> 	    int offset = fieldName[0 .. 1] - 'x';
> 	    if (args.length != 0)
> 	    	return data[offset];
> 	    else
> 	    	return data[offset] = args[0];
>     }
> }
>
> Same error.

Just reread and realized I glossed over your mention of static if.

class Vector(int N, T) if (N <= 3) {
     T[N] data;

     this()
     {
     	data[] = 0;
     }

     @property ref T opDispatch(string fieldName, Args ...)(Args 
args)
         if (Args.length < 2 && fieldName.length == 1 && 
toOffset(fieldName) < N)
     {
	    int offset = fieldName[0 .. 1] - 'x';
	    static if (args.length != 0)
	    	return data[offset];
	    else
	    	return data[offset] = args[0];
     }
}

Still the same problems.