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> In the end it turned out that .NET's reified generics were a mistake Do you have any resources that explain this point further? Reified generics have often

by tomp 8y ago

> In the end it turned out that .NET's reified generics were a mistake Do you have any resources that explain this point further? Reified generics have often been praised as the thing that CLR got right (and JVM got wrong). I never understood fully why that is, especially since other languages with generics (e.g. Haskell and OCaml) don't have anything reified (although in all honesty also don't have RTTI so it's really not necessary).

pron 8y ago
Erasure makes it easy for Java, Kotlin, and Clojure share code and data structures without costly runtime conversions. Languages like Scala and F# have had trouble implementing features on the CLR because of reification, and take a look at what Python and Clojure on the CLR have to go through for interop. I know some people think that say they like reified generics in C#, but those are mostly people who aren't aware of what cost to the entire ecosystem they're paying in exchange to what is a minor convenience in C#. BTW, reification of reference-type generics is not to be confused with specializing collections for value types ("arrays-of-struct") an extremely important feature that CLR indeed has, and Java is now working on getting.
eropple 8y ago
"Mistake" is a strong word, and I would disagree with it. But when building extensible libraries and systems I do often find myself wanting to pass around a List<Something<?>>, which isn't doable without writing a second generic interface or the like. On the flip side, in Java (or, these days, Kotlin), a type-erased generic can be mediated more easily because passing a Class is easier than adding a second interface. Part of it is that a lot of that stuff is gamedev-related, for me. It's not the biggest thing in the world, but for a lot of the stuff I find myself writing in C#, I find myself wishing for type erasure to make throwing data around a little easier. On the other hand, though, when writing web stuff on the JVM--I absolutely will not waste my time doing this in .NET, ASP.NET Core is not very good and EF Core is awful--I often wish for type reification, so it's just a horses-for-courses thing.

by tomp 8y ago

pron 8y ago

Erasure makes it easy for Java, Kotlin, and Clojure share code and data structures without costly runtime conversions. Languages like Scala and F# have had trouble implementing features on the CLR because of reification, and take a look at what Python and Clojure on the CLR have to go through for interop. I know some people think that say they like reified generics in C#, but those are mostly people who aren't aware of what cost to the entire ecosystem they're paying in exchange to what is a minor convenience in C#. BTW, reification of reference-type generics is not to be confused with specializing collections for value types ("arrays-of-struct") an extremely important feature that CLR indeed has, and Java is now working on getting.

eropple 8y ago

"Mistake" is a strong word, and I would disagree with it. But when building extensible libraries and systems I do often find myself wanting to pass around a List<Something<?>>, which isn't doable without writing a second generic interface or the like. On the flip side, in Java (or, these days, Kotlin), a type-erased generic can be mediated more easily because passing a Class is easier than adding a second interface. Part of it is that a lot of that stuff is gamedev-related, for me. It's not the biggest thing in the world, but for a lot of the stuff I find myself writing in C#, I find myself wishing for type erasure to make throwing data around a little easier. On the other hand, though, when writing web stuff on the JVM--I absolutely will not waste my time doing this in .NET, ASP.NET Core is not very good and EF Core is awful--I often wish for type reification, so it's just a horses-for-courses thing.