• Cabal <cabalN05P4M myrealbox.com> Jul 22 2004
• Cabal <cabalN05P4M myrealbox.com> Jul 22 2004
• Stewart Gordon <smjg_1998 yahoo.com> Jul 22 2004
• Cabal <cabalN05P4M myrealbox.com> Jul 22 2004
• Sean Kelly <sean f4.ca> Jul 22 2004

Cabal <cabalN05P4M myrealbox.com> writes:

I have a ragged array hashmap ('int[][char[]] myArray') on which I would
*like* to be able to lookup the 'int[]' part and do operations on its
attributes. Eg...

,----[  ]
| int[] myRow = myArray["test"];
| if (myRow.length <= idx) myRow.length = idx + 1;
| myRow[idx] = 10;
| ...
| // other code
| ...
| int myInt = myArray["test"][idx]      // Bang! ArrayBoundsError
`----

Unfortunately I can't seem to find any way to take a reference to the
'int[]' parts I want to manipulate. Operating on the slices produced by the
above code leaves the original array attributes as they were.

Cabal <cabalN05P4M myrealbox.com> writes:

For the pendants before you start :) I know that its not a hashmap, its a D
associative array - it just didn't read right and the terminology doesn't
really have a bearing on the issue at hand.

Cabal wrote:

 I have a ragged array hashmap ('int[][char[]] myArray') on which I would
 *like* to be able to lookup the 'int[]' part and do operations on its
 attributes. Eg...
 
 ,----[  ]
 | int[] myRow = myArray["test"];
 | if (myRow.length <= idx) myRow.length = idx + 1;
 | myRow[idx] = 10;
 | ...
 | // other code
 | ...
 | int myInt = myArray["test"][idx]      // Bang! ArrayBoundsError
 `----
 
 Unfortunately I can't seem to find any way to take a reference to the
 'int[]' parts I want to manipulate. Operating on the slices produced by
 the above code leaves the original array attributes as they were.

Stewart Gordon <smjg_1998 yahoo.com> writes:

Cabal wrote:

 I have a ragged array hashmap ('int[][char[]] myArray') on which I would
 *like* to be able to lookup the 'int[]' part and do operations on its
 attributes. Eg...


 Unfortunately I can't seem to find any way to take a reference to the
 'int[]' parts I want to manipulate. Operating on the slices produced by the
 above code leaves the original array attributes as they were.


I think you need to either feed the result back into the array, or take 
a pointer.

     myArray["test"] = myRow;

after the modification.  Alternatively, try

----------
int[]* myRow = &myArray["test"];
if (myRow.length <= idx) myRow.length = idx + 1;
(*myRow)[idx] = 10;
----------

I don't know if this'll actually work, and I'm not in a position to test 
it at the mo....

Stewart.

-- 
My e-mail is valid but not my primary mailbox, aside from its being the 
unfortunate victim of intensive mail-bombing at the moment.  Please keep 
replies on the 'group where everyone may benefit.

Cabal <cabalN05P4M myrealbox.com> writes:

Thanks for that Stewart. Works a treat. I didn't consider using pointers
with my D head on :)

Stewart Gordon wrote:

 Cabal wrote:
 
 I have a ragged array hashmap ('int[][char[]] myArray') on which I would
 *like* to be able to lookup the 'int[]' part and do operations on its
 attributes. Eg...


 Unfortunately I can't seem to find any way to take a reference to the
 'int[]' parts I want to manipulate. Operating on the slices produced by
 the above code leaves the original array attributes as they were.


 I think you need to either feed the result back into the array, or take
 a pointer.
 
      myArray["test"] = myRow;
 
 after the modification.  Alternatively, try
 
 ----------
 int[]* myRow = &myArray["test"];
 if (myRow.length <= idx) myRow.length = idx + 1;
 (*myRow)[idx] = 10;
 ----------
 
 I don't know if this'll actually work, and I'm not in a position to test
 it at the mo....
 
 Stewart.
 

Sean Kelly <sean f4.ca> writes:

In article <cdo8mi$lah$1 digitaldaemon.com>, Stewart Gordon says...
I think you need to either feed the result back into the array, or take 
a pointer.

     myArray["test"] = myRow;

after the modification.  Alternatively, try

----------
int[]* myRow = &myArray["test"];
if (myRow.length <= idx) myRow.length = idx + 1;
(*myRow)[idx] = 10;
----------


I've been wondering if it might make sense to offer a reference type specifier.
So far I can think of two ways of doing it without introducing an additional
keyword:

// possibly confusing as this looks like a normal alias call
alias int[] myRow = myArray["test"];

// a bit weird but closer in meaning to what we want to do
inout int[] myRow = myArray["test"];

In both cases the variable would have to be assigned when declared, and it could
not be reassigned afterwords.  ie. it would work just like a reference in C++.


Sean