[Issue 3474] PATCH: Implement opDollar for struct and class indexing operations

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=3474



--- Comment #3 from Andrei Alexandrescu <andrei at metalanguage.com> 2009-11-05 09:18:44 PST ---
(In reply to comment #2)
> (In reply to comment #1)
> > Great!
> > 
> > Any chance we can use "length" instead of "opDollar" throughout? It would
> > instantly match what arrays are currently doing and it would be a closer
> > description of the semantics of the operation.
> 
> Yes, the name doesn't make any difference.
> Although length() looks natural, I think length!(1)() looks a bit clumsy?
> The one-dimensional case is a degenerate form of the multi-dimensional case.
> Moreover, I suspect the template is not the interface you want in most cases:
> you often want to iterate over the dimensions. Probably in most cases, it'd be
> defined like:
> 
> int opDollar(int n)() { return dim[n]; }
> 
> Also there may be problems if you want to be able to use .length to change the
> dimensions.
> 
> BTW you can use aliases. This works:
> 
> struct Foo 
> {
>    int x;
>    int length() { return x; }
>    alias length opDollar;
>    int opIndex(int k) { return x*k; }  
> }
> 
> void main()
> {
>    Foo f = Foo(7);
>    int x = foo[$-5];
>    assert(x== 2*7);
> }

I understand and have no further comments. Let's go with opDollar.

(One suggestion if I may :o). In the 1-dimensional case, of a type defines no
opDollar but does define length... you may want to rewrite $ to length. But
probably that's too complicated a rule already.)

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