There's `fold` for things like that.

# announcements

[karelpeeters]

There's fold for things like that.

[Shawn]

maybe reduce since the transform is just acc + next until the end?

[karelpeeters]

Doesn't work for empty lists!

[Shawn]

oh, interesting - that makes sense, but is there not a safe way to call reduce on a potentially empty list?

[Shawn]

or at least something more idiomatic than if (list.isEmpty()) ... else reduce ...?

[edwardwongtl]

Maybe sth like this?

list.run {
  if (it.isEmpty) return 0
  else return it.reduce(...)
}

[Shawn]

that’s just what I wrote but wrapped in a run block

[Shawn]

you’d just

return if (list.isEmpty()) BigDecimal(0) else list.reduce { ... }

[Shawn]

which is fine, I suppose, it just feels a little funny to me that reduce is kinda unsafe in that regard

[Shawn]

but I suppose there isn’t a good alternative like there is with fold

[karelpeeters]

reduce is safe, it just returns null if empty.

[karelpeeters]

list.reduce(...) ?: BigDecimal.Zero is the same as the fold way.

[marstran]

It doesn't return null if it's empty. It throws an `UnsupportedOperationException`: https://github.com/JetBrains/kotlin/blob/5c26b0ea6f4810fbc78e0d263cea6ef0f3fd7087/libraries/stdlib/common/src/generated/_Collections.kt#L1708

[karelpeeters]

Damm that is a strange design decision.