JAPL - Just Another Programming Language

JAPL is an interpreted, dynamically-typed, garbage-collected, and minimalistic programming language with C- and Java-like syntax.

J.. what?

You may wonder what's the meaning of JAPL: well, it turns out to be an acronym for Just Another Programming Language, but beware! Despite the name, the pronunciation is the same as "JPL".

Disclaimer

This project is currently a WIP (Work in Progress) and is not optimized nor complete. The design of the language may change at any moment and all the source inside this repo is alpha code quality, for now.

For other useful information, check the LICENSE file in this repo.

JAPL is licensed under the Apache 2.0 license.

Project roadmap

In no particular order, here's a list that is constantly updated and that helps us to keep track of what's done in JAPL:

• Parsing/Lexing
• Type system (string, integer, float)
• Builtin collections (arraylist, mapping, tuple, set)
• Builtin functions (print, etc)
• An import system
• Control flow (if/else)
• Loops (for/while)
• Comparisons operators (>, <, >=, <=, !=, ==)
• Casting with the as operator
• Modulo division (%) and exponentiation (**)
• Bitwise operators (AND, OR, XOR, NOT)
• Simple optimizations (constant string interning, singletons caching)
• Garbage collector (Mark & Sweep)
• Operations on strings (addition, multiplication -> TODO both sides)
• Functions and Closures
• Functions default and keyword arguments
• An OOP system (class-based)
• Global and local variables
• Explicit scopes using bracket
• Native asynchronous (await/async fun) support
• Bytecode optimizations such as constant folding and stack caching
• Arbitrary-precision arithmetic
• Multi-line comments /* like this */ (can be nested)
• Generators
• A standard library
• String slicing, with start:end syntax as well
• Multithreading and multiprocessing support with a global VM Lock like CPython
• Exceptions
• Logical operators (not, or, and, is)
• Basic arithmetic (+, -, /, *)
• Optional JIT Compilation
• Static type checker (compiler module)
• Runtime Type Checking

Contributing

If you want to contribute, feel free to open a PR!

Right now there are some major issues with the virtual machine which need to be addressed before the development can proceed, and some help is desperately needed greatly appreciated!

To get started, you might want to have a look at the currently open issues and start from there

Community

Our first goal is to create a welcoming and helpful community, so if you are so inclined, you might want to join our Discord server and our forum! We can't wait to welcome you into our community :D

A special thanks

JAPL is born thanks to the amazing work of Bob Nystrom that wrote a book available completely for free at this link, where he describes the implementation of a simple language called Lox.

JAPL - Installing

JAPL is currently in its early stages and is therefore in a state of high mutability, so this installation guide might not be always up to date.

Requirements

To compile JAPL, you need the following:

• Nim >= 1.2 installed on your system
• Git (to clone the repository)
• Python >= 3.6 (Build script)

Cloning the repo

Once you've installed all the required tooling, you can clone the repo with the following command

git clone https://github.com/japl-lang/japl

Running the build script

As a next step, you need to run the build script. This will generate the required configuration files, compile the JAPL runtime and run tests (unless --skip-tests is passed). There are some options that can be tweaked with command-line options, for more information, run python3 build.py --help.

To compile the JAPL runtime, you'll first need to move into the project's directory you cloned before, so run cd japl, then python3 build.py ./src and wait for it to complete. You should now find an executable named japl (or japl.exe on windows) inside the src folder.

If you're running under windows, you might encounter some issues when using forward-slashes as opposed to back-slashes in paths, so you should replace ./src with .\src

If you're running under linux, you can also call the build script with ./build.py (assuming python is installed in the directory indicated by the shebang at the top of the file)

Advanced builds

If you need more customizability or want to enable debugging for JAPL, there's a few things you can do.

Nim compiler options

The build tool calls the system's nim compiler to build JAPL and by default, the only extra flag that's passed to it is --gc:markAndSweep. If you want to customize the options passed to the compiler, you can pass a comma separated list of key:value options (spaces are not allowed). For example, doing python3 build.py src --flags d:release,threads:on will call nim compile src/japl --gc:markAndSweep -d:release --threads:on.

JAPL Debugging options

JAPL has some (still very beta) internal tooling to debug various parts of its ecosystem (compiler, runtime, GC, etc). There are also some compile-time constants (such as the heap grow factor for the garbage collector) that can be set via the --options parameter in the same fashion as the nim's compiler options. The available options are:

• debug_vm -> Debugs the runtime, instruction by instruction, showing the effects of the bytecode on the VM's stack and scopes in real time (beware of bugs!)
• debug_gc -> Debugs the garbage collector (once we have one)
• debug_alloc -> Debugs memory allocation/deallocation
• debug_compiler -> Debugs the compiler, showing each byte that is spit into the bytecode

Each of these options is independent of the others and can be enabled/disabled at will. To enable an option, pass option_name:true to --options while to disable it, replace true with false.

Note that the build tool will generate a file named config.nim inside the src directory and will use that for subsequent builds, so if you want to override it you'll have to pass --override-config as a command-line options. Passing it without any option will fallback to (somewhat) sensible defaults

P.S.: The test suite assumes that all debugging options are turned off, so for development/debug builds we recommend skipping the test suite by passing --skip-tests to the build script

Installing on Linux

If you're on linux and can't stand the fact of having to call japl with ./src/japl, we have some good news! The build script can optionally move the compiled binary in the first writeable entry inside your PATH so that you can just type jpl inside your terminal to open the REPL. To avoid issues, this option is disabled by default and must be turned on by passing --install, but note that if in any directory listed in PATH there is either a file or a folder named jpl the build script will complain about it and refuse to overwrite the already existing data unless --ignore-binary is passed!

Environment variables

On both Windows and Linux, the build script supports reading parameters from environment variables if they are not specified via the command line. All options follow the same naming scheme: JAPL_OPTION_NAME=value and will only be applied only if no explicit override for them is passed when running the script