[WIP] Array flatten function

[kzon]

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Category:

• New Feature

Short description:

Add function flatten for converting array of arrays to flat array.
Example:
flatten([[1, 2, 3], [4, 5]]) = [1, 2, 3, 4, 5]

[kzon]

@alexey-milovidov I need your advice. It looks like there is no methods for interpreting individual Fields as arrays of arrays. How we can do it? Do we need new GatherUtils function? Or I missed something about memory layout of Field?

[alexey-milovidov]

interpreting individual Fields as arrays of arrays.

Field can be Array. Array is std::vector<Field>. Array elements can also be Array that means we have multidimensional array.

[alexey-milovidov]

I have completed the implementation, you can read code along with comments.