[bluejekyll]

This definitely seems to vary among different languages, and is something I've always been annoyed with in C++.

Scoping outside the for loop is rarely useful, but often creates bugs. The one case where I like it is for searching an array and wanting the index, but even then it's not necessarily elegant.

[amscanne]

I don't really get why it's seen as "reusing" the memory.

i++ is obviously changed the value of a single i variable. Who thinks it's creating a new i somehow?

[bluejekyll]

I don't see this as whether or not there is literally a new i created or not, but if you have access to i after the loops last bracket. Here's an example:

  for (int i=0; i<10; i++) {
    do_something(i);
  }
 
  // i is still valid which might be 
  //  unexpected and cause a bug

vs. something that would look like this

  {
    int i;
    for (i=0; i<10; i++) {
      do_something(i);
    }
  }

  // usage of i at this point would be
  //  a compiler error

I'd have to come up with a convoluted case, where this would directly cause a bug, but it would be a case where you reuse the variable i, and forget to reinitialize it. Java does the second form, and forces you to declare the variable outside the loop if you want to use it in that context.

[amscanne]

So does Go (use the first form).

Saying "loop variables are scoped outside the loop" is incorrect.

All the gotchas noted stem from the fact that people are using _closures_ in the form of go and defer statements, which capture i by reference unless you pass it as an argument.

I think it's more an issue with closure gotchas (or the fact that go and defer statement aren't viewed that way) than with scoping.

[amscanne]

(Whoops, I mean _second_ form.)