Hi,

I'm going circles... ;) I read a string that contains an array of unknown dimension like:
a = [1,2,3,4] or
a = [[1,2],[3,4]] or
a = [[[1,2],[3,4]],[[5,6],[7,8]]]

With that I want to perform specified operations e.g. also provided on command line.

Because at compile time the dimension of the array is unkown I did not find any possibility to do something like:

auto arr = func(a);

where 'auto func(string str)' should return either a 1D, 2D, 3D array and arr is not locked in an if(){} scope.

Is there any way and What should I'm looking for?

Thanks, thorstein

On Wednesday, 21 February 2018 at 06:45:14 UTC, thorstein wrote:
> Hi,
>
> I'm going circles... ;) I read a string that contains an array of unknown dimension like:
> a = [1,2,3,4] or
> a = [[1,2],[3,4]] or
> a = [[[1,2],[3,4]],[[5,6],[7,8]]]
>
> With that I want to perform specified operations e.g. also provided on command line.
>
> Because at compile time the dimension of the array is unkown I did not find any possibility to do something like:
>
> auto arr = func(a);
>
> where 'auto func(string str)' should return either a 1D, 2D, 3D array and arr is not locked in an if(){} scope.
>
> Is there any way and What should I'm looking for?
>
> Thanks, thorstein

There's std.variant: https://dlang.org/phobos/std_variant

The code would probably be something like:

Algebraic!(int[], int[][], int[][][]) array;

if (value.is1D) {
    array = value.read1DArray();
} else if (value.is2D) {
    array = value.read2DArray();
} else {
    array = value.read3DArray();
}

And you'd grab the type of value you want by array.get!(int[][]).

--
  Simen

On 2/21/18 1:45 AM, thorstein wrote:
> Hi,
> 
> I'm going circles... ;) I read a string that contains an array of unknown dimension like:
> a = [1,2,3,4] or
> a = [[1,2],[3,4]] or
> a = [[[1,2],[3,4]],[[5,6],[7,8]]]
> 
> With that I want to perform specified operations e.g. also provided on command line.
> 
> Because at compile time the dimension of the array is unkown I did not find any possibility to do something like:
> 
> auto arr = func(a);
> 
> where 'auto func(string str)' should return either a 1D, 2D, 3D array and arr is not locked in an if(){} scope.
> 
> Is there any way and What should I'm looking for?
> 

If you want a specific type that the type system cares about, you have to implement every possibility. Then you can use Variant.

But if you want a recursive strategy, where you need the dimensions at runtime only, then you can write a struct with a tagged union which gives you all the info you need:

struct NDimArray
{
   size_t dimensions; // if 0, then this is a value
   union {
   	NDimArray[] elements;
        int value;
   }
}

You can probably figure out the rest. Probably you can eliminate the dimensions field somehow to save space.

This is how things like JSON DOM structures work.

-Steve