The "<array> select <code>" variant would return a new array containing only the elements of "<array>" that "<code>" returns true on:

  [1, 2, 3, 4, 5, 6] select { _x % 2 == 0 } // returns [2, 4, 6]

The new "<array> apply <code>" operator would call the "<code>" function on each element of "<array>", and return a new array with the results of each call. For example:

  [1, 2, 3] apply { _x * 2 } // returns [2, 4, 6]

SQF has always had a version of "count" that worked with predicate functions, so it seems natural that the language would be able to filter a list with a <code> argument too.

These two new commands would replace the very common idiom of looping and building lists. For example, to filter a list in present-day SQF requires:

  private "_tmp";

  _tmp = [];

  {
      if (_x % 2 == 0) then 
      { 
          _tmp pushBack _x; 
      };
  }
  forEach [1, 2, 3, 4, 5, 6];

  _tmp

The commands could also be optimised to avoid the multiple reallocations that existing filtering/applying code generally has due to the use of "pushBack":

• For small lists, "<array> select <code>" could first evaluate the predicates, storing the results in a bit-set (e.g. uint32_t), and then do a single exact array allocation before copying the filtered elements into the new array.
• For all cases, "<array> apply <code>" could allocate the new array with the exact number of required elements.