Hacker News Reader

It looks like you can have three union members, just not nesting (weak) or compatibility between T1|T2 and T1|T2|T3 (probably fine). I'm not convinced about ordering being a problem.

View on HN

Ordering is a problem because there's no good way to handle duplicate members. If you have a generic function `f(T) -> T|A` what is the compiler supposed to do when T = A|B? Return A|B|A breaking the main rule of unions or give up and throw a compile error?

And set unions are supposed to be unordered anyway. You're going against what everyone expects from other languages and basic math.

Reply on news.ycombinator.com