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by flohofwoe
756 days ago
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Just call them "tagged union" or "variant" and suddenly "sum types" are not so rare anymore ;) ...same with "struct", "record" or "tuple" vs "product type". Nobody calls them that except functional programmers and mathematicians, both quite rare specimen in the wider programming world, but nevertheless they are ancient and widely known concepts even among us "peasant coders" ;) |
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Nah, this is a false dichotomy. If a language doesn't have product types but instead resort to declaring variables separately, you don't call that "structs". Similarly, calling tagged unions a sum type is kind of misleading. They are both programming languages, I am sure I can do whatever I can do in A using B.
Why is a "struct" such a powerful concept? Because it is correct by construction. When I declare struct A, I have everything that A should contain. It is impossible to say, oops, I forgot about A::b. Similarly, a sum type as a concept is only useful when the abstraction is very, very solid.
Tagged unions or variants (in C and C++ respectively) is nothing like that. I have a variant A, I checked that that it is B, but oops, I casted it as C. Its your typical TOCTOU (or LOCLOU for line of check, line of use, I guess). std::optional is also like, same with pointers. Proper sum types, like Rust, it is literally impossible for me to get C by mistake.
Obviously, all of this minus some underlying implementation details, unsafe code yadda yadda.
Sorry if I sound aggressive, but I am just tired of "we have A at home, A at home (the most cursed shit)".
Does go have enums? Yea... just declare some global constants like so bro.
SomeEnum_A = 0
SomeEnum_B = 1
SomeEnum_C = 2
Yea..."enums"..
Edit: Oh how can I forget, we had this kind of issue just TODAY in production. No wonder I am so pissed off.