opIndex() may hide opSlice()

[H. S. Teoh via Digitalmars-d]

On Fri, Mar 10, 2017 at 01:07:33AM +0000, XavierAP via Digitalmars-d wrote:
> In their versions without parameters, these two operators would be
> called in the same way. If both are defined, opIndex() is called,
> regardless of lexical definition order, according to my test with DMD.
> 
> If both (again I'm just talking about the overloads with no arguments)
> are defined within the same type, it's the fault of the author. But I
> would think the compiler should complain.
> 
> They can also be inherited, which is sneakier.
> 
> The web reference tersely says under its *Slice* Operator Overloading
> chapter [1]: "To overload a[], simply define opIndex with no
> parameters."
> 
> Should not the overload of opSlice() with no arguments be deprecated?
> Am I missing something?
> 
> 
> [1] https://dlang.org/spec/operatoroverloading.html#array-ops

Using opSlice() for slicing (i.e., arr[]) is old, backward-compatible
behaviour.

The recommended usage is to use opSlice to transform range syntax (i.e.,
arr[1 .. 2]) into a type that opIndex understands, i.e.,

	arr[1, 2..3, 4]

is translated to:

	arr.opIndex(1, arr.opSlice(2,3), 4)


T

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