Lox Modern Cpp

Lox Modern Cpp is a modern cpp (C++17) implement of Lox programming language described in Bob Nystrom's book: Crafting Interpreters. The bytecode virtual machine is implemented by new modern cpp features to make it fast, cache friendly, lightweight and modular.

Lox language

Lox is a programming language described in Bob Nystrom's book: Crafting Interpreters. The syntax is similiar to C, with dynamic types and garbage collector. Folowing is a example to calcute the sum of 10000000.

var sum = 0.0;
var i = 0;
while (i < 10000000) {
    sum = sum + i;
    i = i + 1;
}
print sum;

For more details on Lox's syntax, check out the description in Bob's book.

Release Build

Dependency:

• C++17 standard compaitible compiler (gcc and clang tested)
• cmake (> 3.13)

Build steps:

mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release ..

Usage

Run an interactive REPL interpreter:

./lox

Execute lox source files:

./lox <filename.lox>

Unit tests

Lox Modern Cpp use doctest for unit tests. All lox function tests come from Bob Nystrom's implemenations of Lox. Use following sciprt to run all unit tests and generate the code coverage result:

./coverage.sh

Benchmark

Lox Modern Cpp uses google benchmark for benchmarking. Run lox-benchmark after release build to run the benchmarking:

./benchmark/lox-benchmark

Test on Mac OS X, compiled with Apple clang 11.0.3:

(8 X 3600 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x4)
  L1 Instruction 32 KiB (x4)
  L2 Unified 256 KiB (x4)
  L3 Unified 8192 KiB (x1)

Result of Lox Modern Cpp (Unit: second)

Benchmark	Min.	Max.	Average
sum.lox	0.33	0.35	0.34
fib.lox	1.02	1.03	1.02
equality.lox	1.48	1.49	1.48

Result of Clox, Bob Nystrom's C implementation (Unit: second)

Benchmark	Min.	Max.	Average
sum.lox	0.38	0.38	0.38
fib.lox	0.91	0.91	0.91
equality.lox	1.45	1.46	1.46

Todo

• Classes and Instances
• Methods and Initializers
• Superclasses

Contributing

If you find any error or have a suggestion, please do file an issue or send a pull request. Thank you!