Union Types and Option Types (2025)
29 points by g0xA52A2A 2 days ago | 13 comments
cardboardguru 10 minutes ago
Swift has already answered all these questions.
replyp1necone 4 hours ago
One simple but non obvious (at least to me) trick when implementing tagged unions: put the union discriminator/tag at the end, not the beginning - that way a pointer to a union is also a pointer to the value, no need to increment the pointer to point past the tag after discriminating.
replybeached_whale 3 hours ago
when serializing these things it's generally going to be best to put the tag first though. That way it's cheap to figure out how to parse it.
replygnabgib 2 days ago
(2025) And about CopperLang (203 points, 3 days ago, 120 comments) https://news.ycombinator.com/item?id=50308754
replyks2048 3 hours ago
What is the best source for cross-language description of language features? Eg: “optional types”: which langs have them and how do they work? Same with “union types” etc.
replyDonaldPShimoda 2 hours ago
There's no single oracle for these things, unfortunately. One common citation is "Types and Programming Languages" by Benjamin Pierce (2002), but otherwise people generally just use the nomenclature of a specific language and hope cross-linguistic adventurers will figure it out. I think there's somewhat less variance with more modern languages, though, so in some ways it's less of an issue than it once was.
replytylermk04 3 hours ago
Rosetta code is often helpful. Not exactly for language features, necessarily:
https://rosettacode.org/wiki/Monads/Maybe_monad
replydirewolf20 4 hours ago
i read Onion Types
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