why does (0..0).forEach { ... } iterate once instead of zero times?

# announcements

[df]

why does (0..0).forEach { ... } iterate once instead of zero times?

[ephemient]

(0..0).toList() == listOf(0)

[nanodeath]

0 upto 0 should be the empty list

[df]

I can rephrase it. why does 0..0 not produce an empty list

[ephemient]

0 until 0 is empty

[nanodeath]

because it's an inclusive end bound

[Casey Brooks]

A range defines a closed interval in the mathematical sense: it is defined by its two endpoint values which are both included in the range

https://kotlinlang.org/docs/reference/ranges.html#range

[Nir]

yeah, i was also surprised that kotlin made the simple thing closed. Hopefully this doesn't trigger a holy war 🙂

[nanodeath]

maybe they borrowed it from Ruby

[df]

even though i read it I didn't realize the implications for 0..0 but it makes sense. thanks

[ephemient]

it's challenging to represent Int.MIN_VALUE..Int.MAX_VALUE without using inclusive ends

[Nir]

@ephemient that's a good point I hadn't considered, though I'm not sure that's the most common case (seems like in many of those use cases an infinite range would be simpler)

[ephemient]

but generally it doesn't matter - all of the following are equivalent

0 until list.size
0..list.lastIndex
list.indices

and with the last one you don't even need to think about whether the bounds are inclusive or exclusive

[Nir]

yeah, that's a good point

[nanodeath]

I think I've written 0..(list.size - 1) before. feelsbad.

[Nir]

Ruby uses .. for closed and ... for open, which I didn't know. Kotlin I suppose could probably very easily choose to add ... later... not that it's the highest priority

[Nir]

yeah, i've definitely size-1'ed too

[ephemient]

in a way, Swift's ..< for half-open intervals makes it obvious it's not closed, but... I think it's a bit ugly

[ephemient]

spelling it until in Kotlin is fine with me