Comment by titzer | Hacker News Reader

Comment by titzer | Hacker News Reader

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I used to really love Java, it was my second "real" programming language after C/C++, and GC, type safety, and object orientation really changed the way I thought. I also learned almost all I knew about high-performance VMs (up to 2013) in the context of JVMs.

But these days it seems like Java is engaged in one long apology for the "everything is an object" mindset it started out with. It both took it too far and not far enough. Erased generics were the start of the problem. Parametric types! You were the chosen one! You were supposed to unify the primitive types and the object types! And never adding syntax for function types, just single-method interfaces...just ugly and clunky IMHO.

C# did generics right. Well, almost. "void" isn't a real type, so you can't be generic over it.

It is really important in language design that generics can range over any type. It allows the full combinatorial space. I worked really hard to make the Virgil compiler support arbitrary combinations of tuples, arrays, function types, and all of those work together seemlessly in the polymorphic type system. Everything else is a unfortunate shortcut, IMHO.

Its not universal to all of .NET though.

F# does support this (e.g. Task<unit>) because in F# every function has only one input and one output. Therefore it needs a unit/void type at the lang level at least. This simplification surprisingly results in more power and less code compared to C#. Its part of the base design of the language, and an example of something that is hard to change afterwards in future versions.

In F# overloads for different amounts of type args to a function are not common, unlike C# with different types for each Func<T1, T2, T3, ... TResult> or Java with both Supplier and Function types and needing a custom function type for more args last time I checked. A use case that has come up for me would be to dispatch on variadic template args (e.g. loggers) in a typesafe way without reflection penalty, or looking at some of the libraries using overloads that could be reduced (especially in conjunction with inline for the value type overloads I suspect such as found in LINQ). When I see libraries with overloads for parameters like 'Func<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,TResult>' I think of this. Wherever you see multiple overloads in C#/Java just for the sake of multiple generic arguments; that can often be simplified if required/worth it.

Parametric types and the unification of primitive and reference types is the goal of project valhala.

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