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olox

OCaml implementation of the lox language from Crafting Interpreters (I have never used OCaml before, but I have done some work with Haskell)

Use Jane Street's style guide.

TODOs

  • Think about replacing the stdlib with Jane Street's Core.
    • Why this needs to be thought out: I aim for this to have as few dependencies as possible, relying on easily understood OCaml code for beginners like me who are new to the language (avoiding ppx, etc)
    • This also means that the code is easily to understand and avoids duplication, which I feel it does. The lexer is roughly 150 lines of code, and the parser and interpreter are roughly the same.
  • Figure out a way to return lexing errors and exiting before running the parser.
  • Profile the code

Lessons Learned

  • Files implicitly define a module of their filename.
  • Lists are singly-linked, rather than a contiguous array in memory that is reallocated when full a la Rust's Vec<T>. I presume this is due to the garbage collector, where it is easier to allocate a smaller object in the nursery and point the tail node to that rather than allocating the same list again. Is this slow?
  • Jane Street's replacement standard libraries (Base, Core) avoid raising exceptions unless they're postfixed with _exn.
  • OCaml will automatically run any expression of type unit, so functions called for the purpose of expressing side effects should be of prototype unit -> unit.
  • There is no >>= operator in the standard library, and the let* syntax described in Language extensions isn't actually defined either?
    • Ah, it's just saying that forms of let* bindings were allowed, not that they're defined.
  • I have spent way too much time refactoring code that I didn't like, instead of actually writing more code.

Interpreter Things

  • When synchronizing we want to parse the whole thing, but not interpret it

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