[bigstrat2003]

I think "what problems do they solve that I can't already solve" is the wrong way to look at it. After all, ultimately most language features are just syntactic sugar - you could implement for loops with goto, but it would be a lot less pleasant. I think that unions aren't strictly necessary, but they are a very pleasant to use way of differentiating between different, but related, types of value.

[Quarrelsome]

Ok. I'm just trying to understand what code I'm replacing with them. Like I wanna see the before and after in order to gain the same level of excitment as other people seem to have for them.

Often the explanations just seem rather abstract which makes it harder to appreciate the win, versus the hideous sort of code that might appear when they're misused.

[airstrike]

They are so fundamental to the way I write code I can't imagine ever using a language that does not support them.

"Make invalid states unrepresentable."

[arwhatever]

I might suggest that anyone who wants to make it concrete to go through the article

https://fsharpforfunandprofit.com/posts/designing-with-types...

while visiting https://dotnetfiddle.net and typing the code samples in, experimenting with what manner of changes and additions to the code cause the compilation to fail, and considering how you would leverage those abilities in your everyday development work.

I think this would be even more powerful if you then come back and re-read some of the pro-Union comments in this very thread.

[speed_spread]

The value is realized when you have both discriminated union types _and_ language pattern matching (not regex). Then it's not just a way to structure data but a way to think about how to process it.