It was only intended to be illustrative of thinking about the operation as merging two identical data structures in a manner that produces the result. You cou

It was only intended to be illustrative of thinking about the operation as merging two identical data structures in a manner that produces the result. You could accomplish the it using any technique your codebase prefers be it FP, OOP, &c. (some languages might even handle such an operation natively). In this case, I felt that it was sufficiently close to pseudo code “merge these objects by subtracting identical keys left to right,” but I understand your objection to obscurity. I actually feel that the implementation in this example is fairly unimportant.