digitalmars.D.learn - return type based on content of an array
- thorstein (15/15) Feb 20 2018 Hi,
- Simen =?UTF-8?B?S2rDpnLDpXM=?= (14/29) Feb 21 2018 There's std.variant: https://dlang.org/phobos/std_variant
- Steven Schveighoffer (18/39) Feb 21 2018 If you want a specific type that the type system cares about, you have
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
Feb 20 2018
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, thorsteinThere'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
Feb 21 2018
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
Feb 21 2018