smalltalk VS pika

Working on GST my personnal fork of GNU Smalltalk. I've fixed a small issue regarding the object table in 64 bits you can expect to create much more objects without reaching an out of memory. Also I've improved the VM code specialy the way the objects were GCed and initialized so it brings much more flexibility to change the object layout (adding a new field at the VM level for instance) and added a static assert that will warm the developper ;-)

I just switched Pika to using significant indentation. This is mostly because of how annoying line continuation is in a ML-style language (so f a b syntax) without significant indentation or required semicolons, but you can read more about the reasons for that decision in this section of the README.

Recently, I've been working on adding garbage collection to Pika. I've successfully written an Immix-based garbage collector that works with the LLVM GC support infrastructure, and I'm currently working on integrating the GC with Pika, or really Durin, the dependently-typed intermediate representation that Pika compiles to. Because types are passed around at runtime, objects of unknown type and size can be stored unboxed in polymorphic data structures; but that makes keeping track of type information for heap allocations somewhat harder, because type information needs to be allocated and constructed at runtime in some cases. It's an interesting design problem, because you want constructing type information to be fast; but the GC will run much more often, so maximizing tracing speed by avoiding e.g. indirection in type information is important; and you also want to construct as much type information as possible at compile time and embed it as constants.

I've been working on adding algebraic effects to Pika during the past month. It's turned out to be harder than I thought it would, but I'm almost done - performing and catching one effect at a time works, and the compilation strategy I'm using now (I reimplemented the whole thing after realizing the strategy I was using wouldn't actually work) should be enough to handle multiple effects at once and also effect polymorphism, I just have to get those working in the elaborator.

After taking a break from Pika, my dependently-typed ML for systems programming, during the month of January, I've started working on it again by getting recursion to work properly. I'm planning on starting to implement algebraic effects next, and an Immix-based garbage collector for boxed values after that. Here's what my current plan for algebraic effects looks like: