A C++ implementation of a Lox compiler & VM & bytecode interpreter based on Bob Nystrom's book Crafting Interpreters (craftinginterpreters.com) with further optimizations and extensions including:
- Extended bytecode, which yields increased performance and adds support for compiling more constants.
- Custom Memory Manager with custom allocator support.
The specification of Lox can be found in chapter 3 of Crafting Interpreters.
TL;DR; Lox is:
- Dynamically typed (similar to Python) "everything is an object". With 5 built-in data types booleans, numbers (double precision floats), strings, nil
- Garbage Collected
- Supports closures
- . . .
The following snippet shows a recursive function to calculate fibonnaci numbers:
fun fib(n) {
if (n < 2) return n;
return fib(n - 2) + fib(n - 1);
}
print "The 35th fibonnaci number is:";
print fib(35);
More examples can be found in the benchmarks directory.
cLoxpp is fully functioning and all language features of Lox are supported
cloxpp passes all unit tests from munificient/craftinginterpreters (except 2 which it's expected to fail, since it supports larger constant pools for chunks than the interpreter from craftingerpreters). Note that the unit tests requires an older (dart 2.X) than the default version of the Dart SDK to run.
| OS | Tests Passed* |
|---|---|
| Mac OS | 244/244 |
| Linux | 244/244 |
| Windows | Not tested |
*There are 246 unit tests in the dart test suite but two of them tests for correct error messages when chunks are too large, which is chunks with more than 256 elements. However, cloxpp supports long chunks with up to 2^24=16,777,216 elements, thus it "fails" two tests, which is expected and not included in the table.
cLoxpp uses CMake as it's build system. The target to build is cloxpp from the top level CMakeLists.txt. Example commands to build cloxpp for Mac OS, Linux, and Windows are given below.
If you want to build the cloxpp on linux the easiest way is to navigate to the cloxpp directory and execute the command
cmake -DCMAKE_BUILD_TYPE=Release -S . -B cmake-build-release
followed by the command
cmake --build cmake-build-release --target cloxpp
The cloxpp executable is then found at cmake-build-release/cloxpp
Alternatively, it's possible to build cloxpp from outside the source directory by using the same cmake commands as above, but in addition also specifying the paths to the build directory
cmake -DCMAKE_BUILD_TYPE=Release -S /path/to/cloxpp/source/directory -B /path/to/build/directory
followed by the command
cmake --build /path/to/build/directory --target cloxpp
On windows the program can be built using the command
cmake -S /path/to/source/directory/ -B /path/to/build/directory
followed by
cmake --build /path/to/build-dir --config Release --target cloxpp
The VM can be run as an interpreter in a shell by the command
./cloxpp
Alternatively a lox script can be executed by the command:
./cloxpp [script name]
The benchmark directory contains a benchmarking
script benchmark.py written in Python.
The script can be run without any default arguments as:
python benchmark.py
This will execute each lox script in the benchmarks directory 6 times and display mean and standard deviation of the measurements (discarding the 1st iteration as a warmup iteration for every new benchmark).
The benchmark.py script support functionality for writing the output
file
An example output from a Linux Host (AMD 5950X) running the command above is given below:
Lox interpreter benchmark 2024-02-08 22:00:14
interpreter: '/home/tailor/code/compilers/cloxpp/cmake-build-release/cloxpp'
OS: 'Linux'
processor: 'x86_64'
iterations: 5
comment:
--------------------------------------------------------------------------------
benchmark: binary_trees completed [5/5]
mean: 5.31 stdev: 0.08 (0.02 means)
--------------------------------------------------------------------------------
benchmark: equality completed [5/5]
mean: 1.73 stdev: 0.08 (0.05 means)
--------------------------------------------------------------------------------
benchmark: fib completed [5/5]
mean: 1.08 stdev: 0.02 (0.02 means)
--------------------------------------------------------------------------------
benchmark: instantiation completed [5/5]
mean: 2.54 stdev: 0.03 (0.01 means)
--------------------------------------------------------------------------------
benchmark: invocation completed [5/5]
mean: 0.44 stdev: 0.07 (0.15 means)
--------------------------------------------------------------------------------
benchmark: method_call completed [5/5]
mean: 0.24 stdev: 0.01 (0.02 means)
--------------------------------------------------------------------------------
benchmark: properties completed [5/5]
mean: 0.66 stdev: 0.01 (0.02 means)
--------------------------------------------------------------------------------
benchmark: string_equality completed [5/5]
mean: 1.24 stdev: 0.03 (0.02 means)
--------------------------------------------------------------------------------
benchmark: trees completed [5/5]
mean: 1.23 stdev: 0.02 (0.01 means)
--------------------------------------------------------------------------------
benchmark: zoo completed [5/5]
mean: 0.46 stdev: 0.01 (0.02 means)
--------------------------------------------------------------------------------
benchmark: zoo_batch completed [5/5]
mean: 10.00 stdev: 0.00 (0.00 means)