H2JVM – A Haskell Library for Writing JVM Bytecode

H2JVM – A Haskell Library for Writing JVM Bytecode(discourse.haskell.org)

24 points by rowbin 2 days ago | 8 comments

J-Kuhn 42 minutes ago |

At a quick glance, it seems to be missing some hook to resolve class hierarchies - which is needed when merging stacks with different types. Consider

    var foo = expr ? new Foo() : new Bar();

For such an expression, some superclass or superinterface for both Foo and Bar has to be chosen.

What I am curios about is, if the java classfile API[1] provides a good model that could work in Haskell as well - I always had the impression that it was heavily influenced by functional programming, for example it uses "lifting transforms"[2].

PS: Good work on the label resolving part - this model is also used by the Java Classfile API and before it, ASM.

[1]: https://docs.oracle.com/en/java/javase/26/docs/api/java.base... [2]: https://docs.oracle.com/en/java/javase/26/docs/api/java.base...

amarant 39 minutes ago |

This... Confuses me profoundly. My entire career I've worked with Java, and it's mostly a pretty decent language, imo. I think my biggest gripe with Java is the JVM. It's limiting, doesn't really provide any value(the proposed value is portability, but we always run apps in docker containers anyway, so what is it really doing for us?)

I (kinda) get why someone might want to write Haskell rather than Java, but I'm just not sure why you would want to run Haskell on the JVM?

tikhonj 5 minutes ago | |

This project isn't for running Haskell on the JVM, it's for writing a compiler that produces JVM bytecode. You'd use it if you wanted to implement your own JVM language in Haskell or maybe if you wanted to have some kind of JVM-backed domain-specific language embedded in Haskell.

vips7L 23 minutes ago | |

An interesting take.

You get lots of things for free when targeting JVM bytecode. GCs, JITs, interop with one of the largest and most battle tested ecosystems.

pron 10 minutes ago | |

The reason most "serious" or important software is written for the JVM these days is because it gives you an unparalleled combination of performance, productivity, and observability. There's almost no competition if these things are what you need.

rienbdj 25 minutes ago | |

Pretty good performance for low effort is a big win.

internet_points 30 minutes ago |

see also https://github.com/Frege/frege and https://github.com/mchav/froid (though both are kind of dead I guess?)

J-Kuhn 22 minutes ago | |

There is also Idris 2 for JVM (https://github.com/mmhelloworld/idris-jvm)

Frege targets Java source code, which is then compiled by javac - the downside of that approach is you can not preserve the line numbers for debug information.