Comment by pjmlp

2 days ago

Actually no it didn't, DLR was created exactly to support dynamic languages on the CLR.

Nowadays largely abandoned, and I think not everything survived the transition from .NET Framework into modern .NET.

8 comments

pjmlp

The DLR is just a shared library. It never changed anything about the CLR under the hood nor did it change anything about how Generics worked in the CLR (being the most relevant part of the thread here). IronPython could instantiate Generics just fine, and did just fine working with them.

The DLR is not "abandoned" so much as "complete". Everything did survive the transition into modern .NET and IronPython 3.4.2 runs just fine on .NET 6+ [1]. (For those trapped on the ugly side of the Python 2/3 split, even IronPython 2.7.12 runs on .NET 6.) Most of the "magic" of the DLR is shared with C# Linq in interesting ways (the System.Linq.Expressions AST) and sort of "has to survive" if only to properly support IQueryable<T> (and wilder relatives like IQbservable<T>, the Q is not a typo) even if most people aren't actively using DLR languages today (nor that much usage of C#'s `dynamic` keyword).

IronPython is a community supported (truly open source) language so doesn't get as much attention now as it did in the brief "first party" support era, so some may call that "abandoned" but F# has always lived in that gray space where it is primarily "community supported" more than "officially supported" by a dedicated team at Microsoft.

[1] https://github.com/IronLanguages/ironpython3/releases/tag/v3...

pjmlp 2 days ago
The addition of dynamic, and JIT being aware of IDynamicMetaObjectProvider also mattered.
Even though most of the communication around dynamic was about COM support and Excel.
- WorldMaker 2 days ago
  
  IDynamicMetaObjectProvider mostly just caches and returns System.Linq.Expressions for various asks, so again most of the JIT awareness is still just System.Linq.Expressions awareness.
  The COM support is by implementing IDynamicMetaObjectProvider in a cross-language reusable base class.
  The C# `dynamic` keyword adds some smarts about IDynamicMetaObjectProvider to the C# compiler, but those smarts were never seen to be needed as a low level tool in the CLR itself. And again, once the C# compiles the IDynamicMetaObjectProvider calls, those mostly just result in System.Linq.Expressions for the JIT compiler to optimize in the same way it optimizes other usages of Linq.

kuhsaft 2 days ago

Yeah, that’s a different issue. Statically-typed languages, including type-erased languages, are fine on the CLR. Dynamically-typed languages are a different beast.

I suppose DLR would be comparable to GraalVM/Truffle.

The difficulty of implementing a dynamically-typed language directly on the CLR and JVM are about the same. Though, it would probably be more efficient on the CLR with access to lower level operations for memory management.

I think an interesting project would be to implement a CIL interpreter on GraalVM.

pjmlp 2 days ago
DLR inspired the addition of invokedynamic opcode on the JVM, which is actually the foundation for how lambdas get generated, many still think nested anonymous classes are used.
GraalVM already handles LLVM bitcode, much cooler than plain MSIL.
And here there is another example where Java ecosystem ends up being better.
MSR had a compiler framework similar to GraalVM, called Phoenix, it was going to replace VS, LLVM style, instead it died and what is left are a couple of research papers.
- cogman10 2 days ago
  
  > many still think nested anonymous classes are used.
  Anonymous classes are still used (sometimes). It simply depends on the circumstance of the lambda.
  For example, this will result in a new anonymous class being generated.
  void foo(String s) { stream.filter(i->s.equals(i)); }
  The class gets generated to capture the `s` variable. Indy gets used in the `filter` method because the incoming lambda or method reference could be several types of method calls. For example, a constructor, an instance method, or a static method (I believe there are few more in the JVM bytecode).
  What won't generate a new anonymous class is this sort of lambda
  stream.filter(i->"foo".equals(i));
  That will generate a new method on the parent class which ultimately gets called. Since nothing is captured it can be directly called without a new instance being created.
  
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