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Nested functions/ nested functions as data: Top or flop?

I'd say if you're in that situation, `fun interfaces` make a lot more sense, and will surely look nicer as a type

By "nested functions" do you mean (a) functions defined in the body of another function, or (b) function-typed parameters? If you mean (a), then how are fun interfaces (suggested by Youssef) of use in this situation?

I assumed he meant the second because he specified "as data", but maybe I misinterpreted. Nested functions are okay. Sometimes they can result in a bit of performance overhead, but most of the time they're okay

React uses nested functions excessive. Therefore I asked myself, if they are useful in some way in backend. I think most of the time they make code much less readable and debugable.

But I also had the case in codewars, where they where pretty useful:
```val f : (Int, Int, Int) -&gt; Int = { x: Int, mult: Int, inc: Int -&gt; mult*x+inc }```

I would suggest writing these as top-level functions, or at least with the `fun` syntax while nested:
```fun f(x: Int, mult:Int, inc:Int) = mult * x + inc```