News for hackers. Stuff that matters.

A comment on dotNET (OK, C#) gets union types. Parent comment

Re:dotNET (OK, C#) gets union types by jafffsuds on Sunday May 24, 2026 @12:11AM (#48254295)
What you are describing is something different called a disjoint union which will maintain the identities of the left and right values when there is overlap.

The C# unions appear to behave like unions, not disjoint unions.

[ Parent | on HN ]
Re:dotNET (OK, C#) gets union types by bertylicious on Sunday May 24, 2026 @03:05AM (#48255167)
My mistake. I see my oversight now. `Either String String` is not equivalent to `String | String`, but to `Left String | Right String`. The same must be done for the C# version.

You are correct that this requires support for disjoint unions (aka tagged unions), which Haskell always had and C# will soon have.

[ Parent | on HN ]