Proposal: Make [][x] and [][a..b] illegal (reserve for multidimensional arrays)

[Oskar Linde]

Bill Baxter wrote:
> Oskar Linde wrote:
>> Bill Baxter wrote:
>>
>>> Anyway, f[i][j][k] syntax is much more difficult to read than 
>>> f[i,j,k].  So I think the latter is what we should be shooting for.
>>
>> I agree, and for what it is worth it is possible to implement 
>> multidimensional indexing and slicing for UDTs today. The only thing 
>> lacking is the ability to use the .. and $ tokens. For example:
>>
>> f[i, all, all, j, all, end-1, all, range(1, end)]
>>
>> gets translated into quite optimal code. The only variables that get 
>> passed to the indexing function is (i,j,1,1) and no temporaries need 
>> to be created. I guess that with some additional compiler supported 
>> sugaring, the above could become something like:
>>
>> f[i, .. , .. , j, .. , $-1, .. , 1..$]
>>
> 
> Now if you would just put all that goodness on Dsource or somewhere 
> where the rest of us can appreciate it... :-)

OK. I extracted it from my sources, stripping it from most external 
dependencies. Operator overloading is also stripped and most non-essentials:

http://www.csc.kth.se/~ol/multiarray.zip

The result is basically a simple demonstration of a strided 
multidimensional array slice type.

Indexing/slicing is done in such a way that:

f[a,b,c] is identical to
f[a][b][c]
f[a,b][c]
f[a][b,c]

Don's global __dollar idea is implemented, but not int[2] slices (can't 
do them easily as things are now).

f[i, all, all, j, all, $-1, all, range(1, $)]

All indexing expressions are inlined by GDC at least. Since they are 
inlined, there is probably no need to make "all" a distinct type rather 
than range(0,$), but that is how it is now.

Iteration is very sub-optimal since it relies on opApply, that neither 
GDC nor DMD can inline (as far as I know).

opIndex and opIndexAssign are implemented so they return the ElementType 
rather than a 0-dimensional array when all dimensions are collapsed.

Since I just rewrote parts of it right now without keeping my unit 
tests, the implementation is very unlikely to be bug free. :)

-- 
Oskar