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I don't understand where you come from with your argument. Recursion is also producing results that are "wrong answers" although I prefer to call them partial

I don't understand where you come from with your argument. Recursion is also producing results that are "wrong answers" although I prefer to call them partial results. Just like a loop that is producing partial results as long as it has not finished yet.

wizofaus 4y ago
Out of curiosity is there actually any chipset with the algorithmic ability to add more than 2 numbers altogether in one operation (without having to store intermediate results)? I'd also think looping is far closer than recursion to how we tend to manually calculate things (either entirely in our heads or using a pen & paper or even a basic calculator). (Edit: looks like a number of other posters have made the same point already, but in dead/downvoted posts, not sure why...)
- twawaaay 4y ago
  Chips have ability to run vector operations that can add a bunch of numbers. The issue is that recursion in software development is relatively rarely about arithmetic operation. For example, you might want to traverse a tree of objects (like a filesystem folder) to run some operation on them, etc. In this case the intermediate information is pointers to where you are currently processing various folders in your tree structure, etc. In a loop you would have to create a data structure to hold these. In recursive function this would typically be spread in multiple frames on your stack pointing to objects in your heap.
  - wizofaus 4y ago
    Vector operations that perform the same fixed addition to each element, yes, but that's not really the same thing. And yes I'm very much in agreement that the real power of recursive algorithms is when working with tree-like data structures.
    - twawaaay 4y ago
      Your question was, and I quote: > is there actually any chipset with the algorithmic ability to add more than 2 numbers altogether in one operation (without having to store intermediate results) I was just answering your question. I am not responsible for quality of your questions. What you do is you posted a question but had something else in mind. You got an answer but that answer does not match the question you had in your mind so now you think it is ok to berate somebody for not being able to read your mind.
      - wizofaus 4y ago
        My understanding is those vector operations don't , in fact, add more than 2 numbers together, but rather simultaneously add lots of pairs of numbers. Happy to be corrected and no berating intended.
- mrkeen 4y ago
  > Out of curiosity is there actually any chipset with the algorithmic ability to add more than 2 numbers Perhaps? But this would be like asking if there was a chipset that can work without branching because of someone mentioning "GOTO bad". > I'd also think looping is far closer than recursion to how we tend to manually calculate things It's not the looping I mind, it's the mutation.
  - wizofaus 4y ago
    If there were such an ability at the machine language level, it would be a strong argument against expressing the addition of a set of numbers using either a loop or recursion. I don't really see that either manner of expressing such an operation is always preferable, and would rather simply use a built-in language or feature (e.g. reduce) that the compiler/interpreter is free to translate into the most appropriate machine instructions for the given hardware.
mrkeen 4y ago
> Recursion is also producing results that are "wrong answers" Not true. If you share your copy of: answer = sum [1..10] One viewer might see: answer = 3 + sum [3..10] and another viewer might see: answer = 6 + sum [4..10]. They may be "partial results", but they are correct and equal to each other. This is different from one viewer seeing 3 and another viewer seeing 6. "But can't you just hide the partial result until it's ready?" Sure. Get rid of class fields and getters(). I'm happy to. Are you?
- mpweiher 4y ago
  You tend to not put temporary results of loops in instance variables, but in local variables. Which aren't visible externally at all. And yes, if you do have that exceptional case of a complex algorithm that needs to store partial results in ivars as they are required by different methods and inconvenient to pass around individually, those ivars tend to not be exposed. In fact, you'd more likely create a separate context object that you pass around, so also not visible externally.
  - mrkeen 4y ago
    > You tend to not put temporary results of loops in instance variables, but in local variables. Which aren't visible externally at all. Cool! Then it follows: If a result is not temporary, then it can be immutable. Properly immutable, not just final. If a result is temporary, then it is not to be visibly external at all. Not as a field, and not via any getter. I could live with that.
    - mpweiher 4y ago
      That doesn't follow. Objects do (much) more than implement algorithms in loops. In fact, I'd say that if you're doing algorithms as objects, you're almost certainly Holding it Wrong™. Algorithms tend to be perfectly fine contained in a method of an object.
- Joker_vD 4y ago
  Have you heard about the concept of "loop invariant"? s = 0 i = 0 // Invariant: before and after every iteration, s is equal to sum of [0..i] // End condition: i == n while i != n: s += i i += 1 // Here, i == n and so s is a sum of [0..n] because the invariant still holds That's how loops were supposed to be thought about (and written) since the 70ies, and it's more or less equivalent to induction which is what you're supposed to use when you think about recursive functions.

wizofaus 4y ago

Out of curiosity is there actually any chipset with the algorithmic ability to add more than 2 numbers altogether in one operation (without having to store intermediate results)? I'd also think looping is far closer than recursion to how we tend to manually calculate things (either entirely in our heads or using a pen & paper or even a basic calculator). (Edit: looks like a number of other posters have made the same point already, but in dead/downvoted posts, not sure why...)

twawaaay 4y ago
Chips have ability to run vector operations that can add a bunch of numbers. The issue is that recursion in software development is relatively rarely about arithmetic operation. For example, you might want to traverse a tree of objects (like a filesystem folder) to run some operation on them, etc. In this case the intermediate information is pointers to where you are currently processing various folders in your tree structure, etc. In a loop you would have to create a data structure to hold these. In recursive function this would typically be spread in multiple frames on your stack pointing to objects in your heap.
- wizofaus 4y ago
  Vector operations that perform the same fixed addition to each element, yes, but that's not really the same thing. And yes I'm very much in agreement that the real power of recursive algorithms is when working with tree-like data structures.
  - twawaaay 4y ago
    Your question was, and I quote: > is there actually any chipset with the algorithmic ability to add more than 2 numbers altogether in one operation (without having to store intermediate results) I was just answering your question. I am not responsible for quality of your questions. What you do is you posted a question but had something else in mind. You got an answer but that answer does not match the question you had in your mind so now you think it is ok to berate somebody for not being able to read your mind.
    - wizofaus 4y ago
      My understanding is those vector operations don't , in fact, add more than 2 numbers together, but rather simultaneously add lots of pairs of numbers. Happy to be corrected and no berating intended.
mrkeen 4y ago
> Out of curiosity is there actually any chipset with the algorithmic ability to add more than 2 numbers Perhaps? But this would be like asking if there was a chipset that can work without branching because of someone mentioning "GOTO bad". > I'd also think looping is far closer than recursion to how we tend to manually calculate things It's not the looping I mind, it's the mutation.
- wizofaus 4y ago
  If there were such an ability at the machine language level, it would be a strong argument against expressing the addition of a set of numbers using either a loop or recursion. I don't really see that either manner of expressing such an operation is always preferable, and would rather simply use a built-in language or feature (e.g. reduce) that the compiler/interpreter is free to translate into the most appropriate machine instructions for the given hardware.

mrkeen 4y ago

> Recursion is also producing results that are "wrong answers" Not true. If you share your copy of: answer = sum [1..10] One viewer might see: answer = 3 + sum [3..10] and another viewer might see: answer = 6 + sum [4..10]. They may be "partial results", but they are correct and equal to each other. This is different from one viewer seeing 3 and another viewer seeing 6. "But can't you just hide the partial result until it's ready?" Sure. Get rid of class fields and getters(). I'm happy to. Are you?

mpweiher 4y ago
You tend to not put temporary results of loops in instance variables, but in local variables. Which aren't visible externally at all. And yes, if you do have that exceptional case of a complex algorithm that needs to store partial results in ivars as they are required by different methods and inconvenient to pass around individually, those ivars tend to not be exposed. In fact, you'd more likely create a separate context object that you pass around, so also not visible externally.
- mrkeen 4y ago
  > You tend to not put temporary results of loops in instance variables, but in local variables. Which aren't visible externally at all. Cool! Then it follows: If a result is not temporary, then it can be immutable. Properly immutable, not just final. If a result is temporary, then it is not to be visibly external at all. Not as a field, and not via any getter. I could live with that.
  - mpweiher 4y ago
    That doesn't follow. Objects do (much) more than implement algorithms in loops. In fact, I'd say that if you're doing algorithms as objects, you're almost certainly Holding it Wrong™. Algorithms tend to be perfectly fine contained in a method of an object.
Joker_vD 4y ago
Have you heard about the concept of "loop invariant"? s = 0 i = 0 // Invariant: before and after every iteration, s is equal to sum of [0..i] // End condition: i == n while i != n: s += i i += 1 // Here, i == n and so s is a sum of [0..n] because the invariant still holds That's how loops were supposed to be thought about (and written) since the 70ies, and it's more or less equivalent to induction which is what you're supposed to use when you think about recursive functions.