digitalmars.D.learn - multi-dimensional array whole slicing
- XavierAP (7/7) Apr 22 2017 I can do:
- kinke (4/11) Apr 22 2017 int[3][4] arr = void;
- XavierAP (4/7) Apr 23 2017 Thanks... I think I prefer to write two loops though :p I wish D
- =?UTF-8?Q?Ali_=c3=87ehreli?= (8/15) Apr 23 2017 It took me a while to convince myself that there is no bug here. The
- XavierAP (6/9) Apr 23 2017 Ha, you're right, I hadn't realized.
- =?UTF-8?Q?Ali_=c3=87ehreli?= (12/16) Apr 25 2017 I think it's still consistent because the element type is not int in the...
- XavierAP (18/23) Apr 25 2017 It is consistent, I just miss the possibility to more easily
I can do: int[3] arr = void; arr[] = 1; But apparently I can't do: int[3][4] arr = void; arr[][] = 1; What is the best way? What am I missing?
Apr 22 2017
On Saturday, 22 April 2017 at 20:51:46 UTC, XavierAP wrote:I can do: int[3] arr = void; arr[] = 1; But apparently I can't do: int[3][4] arr = void; arr[][] = 1; What is the best way? What am I missing?int[3][4] arr = void; (cast(int[]) arr)[] = 1; assert(arr[3][2] == 1);
Apr 22 2017
On Saturday, 22 April 2017 at 22:25:58 UTC, kinke wrote:int[3][4] arr = void; (cast(int[]) arr)[] = 1; assert(arr[3][2] == 1);Thanks... I think I prefer to write two loops though :p I wish D you can do in D for custom types)
Apr 23 2017
On 04/22/2017 01:51 PM, XavierAP wrote:I can do: int[3] arr = void; arr[] = 1; But apparently I can't do: int[3][4] arr = void; arr[][] = 1; What is the best way? What am I missing?It took me a while to convince myself that there is no bug here. The problem, as is obvious to others, ;) a whole slice of a whole slice is still the same slice. So it's not possible to go deeper into the element slices. Here is a proof with a simple array: int[] a; static assert(is(typeof(a[]) == typeof(a[][][][]))); Ali
Apr 23 2017
On Sunday, 23 April 2017 at 09:06:35 UTC, Ali Çehreli wrote:It took me a while to convince myself that there is no bug here. The problem, as is obvious to others, ;) a whole slice of a whole slice is still the same slice.Ha, you're right, I hadn't realized. But I still have a problem. For both multi-dimensional and uni-dimensional arrays a[] and a[][] are the same. And yet, a[] has different type in both cases and a[]=1 compiles for uni-dimensional but not for multi-dimensional.
Apr 23 2017
On 04/23/2017 12:04 PM, XavierAP wrote:For both multi-dimensional and uni-dimensional arrays a[] and a[][] are the same. And yet, a[] has different type in both cases and a[]=1 compiles for uni-dimensional but not for multi-dimensional.I think it's still consistent because the element type is not int in the case of multi-dimensional arrays. The following makes sense to me but I haven't profiled it. Otherwise, kinke's solution is perfectly fine in a system programming language. ;) int[3] a; a[] = 1; a[][] = 1; // Same effect int[3][4] b; b[] = [1, 1, 1]; b[][] = [1, 1, 1]; // Same effect Ali
Apr 25 2017
On Tuesday, 25 April 2017 at 20:46:24 UTC, Ali Çehreli wrote:I think it's still consistent because the element type is not int in the case of multi-dimensional arrays. [...] int[3][4] b; b[] = [1, 1, 1];It is consistent, I just miss the possibility to more easily initialize multi-dimensional arrays uniformly in the same way as uni-dimensional ones. I do not mean it would be good to change the current behavior. I think the best solution would be for D to implement built-in truly multi-dimensional arrays like T[,] as well as the existing could maybe even be lowered into jagged arrays (together with their initializations and slicings). But again most people probably don't miss T[,] built-in arrays, specially since we can implement such [,] indexing for custom types. So there's not a strong use case. But actually where I'm using multi-dimensional built-in arrays right now is in the private storage of a custom multi-dimensional type. Then I have the choice of either use them and live with this, but forward indexing transparently; or use uni-dimensional as private storage and map from 2d to linear during indexing...
Apr 25 2017