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"Generics" in Haskell are real, but they're not what is in the .NET lingo called reified. Just like Java does not monomorphise. On the other hand, C#, F# or Ru
by sideeffffect 6y ago
"Generics" in Haskell are real, but they're not what is in the .NET lingo called reified. Just like Java does not monomorphise.
On the other hand, C#, F# or Rust monomorphise (have reified generics).
- DaiPlusPlus 6y agoAre “monomorphism” and “reification” interchangeable terms though? Considering how .NET now has covariant/contravariant generics I wonder if it could be described as having “polymorphic” generics as opposed to monomorphic generics - (unrelated to OOP polymorphism, ofc).
- sideeffffect 6y agoAFAIUI _monomorphisation_ and reification are interchangable. That means, that if I have a polymorphic (generic) class `MyClassA<T>`, the compiler (regardless if it is JIT in the runtime as in C#, or AOT as in Rust) monomorphises (reifies) `MyClassA` for each instantiation of `T`. So `MyClassA<MyClassB>` and `MyClassA<MyClassC>` are distinct classes. For this reason, co-/contra-variance in C# works only for interfaces. Type parameters in classes are invariant. `MyClassA<MyClassB>` and `MyClassA<MyClassC>` are distinct classes, neither sub-/super-class of the other, even if `MyClassB` were a subclass of `MyClassC`.