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Comment by shakow | Hacker News Reader

> "For" loops may now range over integers

The future is now, old man!

      for i := range 10 {

What was the syntax for this before?

     for i := 0; i < 10; i++

Thanks. The new syntax emulates the python `for x in range(10):`.

I must be getting old because I almost wish they didn't add this as it's slightly ambiguous whether it's ranging from [0, 10) or [1, 10] and anything ambiguous is probably going to haunt me at 3am some day

I always just assume it is consistent to whether arrays start at [0] or [1] on whichever language I am working on.

Interestingly, this does not raise any error, rather has no effect.

for i := range -10 { panic(i) }

"yes, please run this loop minus 10 times" - statements dreamed up by the utterly Deranged

Back in my days, you had to do it this way

for i := 0; i <=-10; i++{

  panic

}

Back in my day you would do

    for (size_t i = 0; i < -10; i++) {
        panic
    }

And it would panic 18446744073709551606 times.

Sure, presumably for the same reason a C-style for loop wouldn't do anything weird there either.

> anything ambiguous is probably going to haunt me at 3am some day

Man, I hope you never wondered how ERRNO behaves with CGo or that you didn't miss to update any initialization of that struct you recently added a new field to, that haunts me at 3AM.

It iterates 10 times staring with 0, seems pretty clear that the result is [0,10).

Wish you could do

  for i := range [3:10] {

I think you could write something using the experimental Rangefunc feature that does that.

You can, which makes me wonder why they added the range-over-int functionality when it could have been a function in the proposed iter package:

   for x := range iter.N(10) { ... }

Better yet, you can name it something like `iter.ZeroTo(10)` and it immediately clears up questions about whether it begins from 0 or 1.

My guess because it really doesn't save that many characters compared to

for i:= 3 ; i<10; i++ {}

I didn't count but it might actually be longer.

range 10 is at least shorter

  for i := range [10]struct{}{} {

I'm not sure what the syntax is now; the release notes say "see the spec for details[link]", but in the link I don't see anything in there about using integers as a range expression.

While the phrasing is funny, it's really more "we now have a direct equivalent to 10.times in ruby"

Algol 68 had a loop where pretty much any part was optional, so both "TO 10" and "FOR i TO 10" (if you needed a loop variable) were possible.

(Back when Go came out, there were some Algol 68 comparisons, IIRC)

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