5 ms·

> There, the reference to `i` is being mutated. That's rebinding. Mutation is when you change the state of an object. Variables are not objects. You can't have

> There, the reference to `i` is being mutated. That's rebinding. Mutation is when you change the state of an object. Variables are not objects. You can't have a reference (aka pointer) pointing to a variable.

1718627440 1y ago
> You can't have a reference (aka pointer) pointing to a variable. What? int a; int * p = &a; ?
- ramchip 1y ago
  That's a pointer to an integer.
  - 1718627440 1y ago
    Yes. You claimed you can't have pointers to a variable. I showed how to have a pointer to a variable of type integer.
    - ramchip 1y ago
      If you dereference it you get back an integer, not a variable. A variable is a name that identifies a value; the pointer points to the value, not to the name.
mrkeen 1y ago
I don't know if you're referring to a particular language's peculiarities, but it doesn't really matter. It's mutation. tombert's point (I think) is that in a functional setting, factorial(n) is always factorial(n). In an imperative setting, first it's 1, then 2, then 6, then 24, etc. Here's factorial calculated imperatively in C#. public async Task Factorial() { long primitiveResult = 1L; Wrapped<long> objectResult = new Wrapped<long>(1L); var observer = new Task(ObserveVariable); observer.Start(); for (var i = 2; i <= 15; i++) { primitiveResult *= i; objectResult = new Wrapped<long>(objectResult.Value * i); await Task.Delay(100); } observer.Wait(); return; void ObserveVariable() { while (primitiveResult != 1307674368000 || objectResult.Value != 1307674368000) { Thread.Sleep(100); } } } There are two results (one primitive and one object) to show that it doesn't matter. Maybe there's no such thing as a Reference-to-a-Variable in whatever language you have in mind, but in the above code ObserveVariable refers to a variable (while it mutates).
tombert 1y ago
I mean this is getting into splitting-hairs territory, but I would argue that rebinding is a form of mutation; the variable i is changing as far as the programmer is concerned. If I were to write var i = new Obj(2) // do stuff 1 i = new Obj(3) // do stuff 2 Then yes, that’s technically rebinding and not directly mutating the value in memory, but from “do stuff 2’s” perspective the value has changed. It still acts more or less the same as if it had directly changed.

1718627440 1y ago

> You can't have a reference (aka pointer) pointing to a variable. What? int a; int * p = &a; ?

ramchip 1y ago
That's a pointer to an integer.
- 1718627440 1y ago
  Yes. You claimed you can't have pointers to a variable. I showed how to have a pointer to a variable of type integer.
  - ramchip 1y ago
    If you dereference it you get back an integer, not a variable. A variable is a name that identifies a value; the pointer points to the value, not to the name.

mrkeen 1y ago

I don't know if you're referring to a particular language's peculiarities, but it doesn't really matter. It's mutation. tombert's point (I think) is that in a functional setting, factorial(n) is always factorial(n). In an imperative setting, first it's 1, then 2, then 6, then 24, etc. Here's factorial calculated imperatively in C#. public async Task Factorial() { long primitiveResult = 1L; Wrapped<long> objectResult = new Wrapped<long>(1L); var observer = new Task(ObserveVariable); observer.Start(); for (var i = 2; i <= 15; i++) { primitiveResult *= i; objectResult = new Wrapped<long>(objectResult.Value * i); await Task.Delay(100); } observer.Wait(); return; void ObserveVariable() { while (primitiveResult != 1307674368000 || objectResult.Value != 1307674368000) { Thread.Sleep(100); } } } There are two results (one primitive and one object) to show that it doesn't matter. Maybe there's no such thing as a Reference-to-a-Variable in whatever language you have in mind, but in the above code ObserveVariable refers to a variable (while it mutates).

tombert 1y ago

I mean this is getting into splitting-hairs territory, but I would argue that rebinding is a form of mutation; the variable i is changing as far as the programmer is concerned. If I were to write var i = new Obj(2) // do stuff 1 i = new Obj(3) // do stuff 2 Then yes, that’s technically rebinding and not directly mutating the value in memory, but from “do stuff 2’s” perspective the value has changed. It still acts more or less the same as if it had directly changed.