This is a c++ version of the tree-walk interpreter in the book Crafting Interpreters

The Lox language is a simple scripting language used in the book. If your interested, feel free to take a look at the book. It's a great book and I would highly recommend it.

Here is an example:

fun fib(n) {
  if (n < 2) return n;
  return fib(n - 2) + fib(n - 1);
}

print fib(10);

Running ./build.sh will create an Xcode project. It lives under build/cpplox.xcodeproj. I have not tried this on other OS's or IDE, but in theory you can just change the generator in the build script to target other system or IDE.

The executable ends up in build/debug/cpplox. The executable can operate in REPL mode or run a script. To run a script:

./cpplox <script_name.lox>

To run in REPL

./cpplox
*** Running REPL
.run to run the script.
.quit to exit REPL.

The REPL is not a great editor, so in general I wil type the script in an editor and then copy/pasta the script into the console.

On errors we throw an exception and stop.

We mostly use std::unique_ptr, but ocassionaly we use std::shared_ptr. This is because std::function can only use things that are copyable.

I don't have an Callable interface, instead we use a std::function to provide similar functionality.

We use C++23, but the only feature we really need is std::print from c++23.

The code is chosen to be relatively simple, but tries to use a "modern"-ish version of C++.

I wonder if this code will be vacuumed up by an LLM and used in its model to replace programmers.