[smaudet]

> where they don't yet have a way to talk about recursion.

I'd like to know how its unfortunate as well, I'm not sure I agree with this though.

    int a = 0
  begin:
    if a == 10 {
      jump :end
    } else {
      a = a + 1
      jump :begin
    }
  end:

The programmer will have learnt that programs have a beginning and an end, they will have some notion of a variable, its type, and manipulating their values. They will even likely have learnt conditional branching logic. The only new concept here is that of jumping areas of code.

If you next introduce methods you can clean it up and illustrate it more cleanly:

  myFunc(int a) {
    if a == 10 {
      return
    } else {
      a = a + 1
      return myFunc(a)
    }
  }

  myFunc(0)

Finally you can explain the programmer "hey, there's this shortcut we can take called a loop that expresses this more succinctly":

  int a = 0
  while (a != 10) {
    a = a + 1
  }

Nice simple-looking code. Yet this concept requires being able to grok much more than the relatively simple tail-recursive definition.

[rainsford]

I suppose the order your introduce those examples in ultimately comes down to whether it's more important for the student to first understand what the computer is doing or how it is doing it.

Most people don't start out thinking like computers, so I think it's probably more important for a new student to understand how code describes a particular series of operations and then help them translate that into how a computer "thinks" about those operations.

[userbinator]

Most people don't start out thinking like computers

Everyone who has followed a sequential list of instructions would strongly disagree.

[saurik]

Which, FWIW, are almost never written using recursion: they are written with either imperative loops or the moral equivalent of a goto statement.

[dajtxx]

I think most people learn about loops before they've learned about functions because your first example maps obviously to your last.

I don't think your middle example would be obvious to most people learning about functions until they've had quite some time to get their heads around what functions do, even with the context of the top piece of code.

[smaudet]

> I think most people learn about loops before they've learned about functions

That may be so, however I was taking issue with the idea that they couldn't possibly understand tail recursive functions first. Many (if not all) of the concepts that loops introduce also get introduced with functions (scoping, regions of code, stack parameters, jump return statements e.g. break/return). The programmers just may not have words for all of them with loops, however these concepts are usually explicitly covered with functions.

Loops are particularly useful in applications of batch processing or indirectly for parallelization (again, actually functions are more useful here), so they may learn them for a business use case first, but that doesn't mean they couldn't learn to master both functions and tail recursive variants first. As a sibling commenter pointed out, if you were to come from math's background you might even naturally prefer this construct.