Loxi

Bytecode interpreter for the Lox language with a mark and sweep garbage collector, based on the second half of Crafting Interpreters by Robert Nystorm.

You can use the WASM playground hosted on GitHub Pages.

Lists

Also supports lists and has additional native functions. Credits to Caleb Schoepp's blog.

var l = [1, 2, 3, 4, 5];
print "List";
print l; // [1, 2, 3, 4, 5]

print "Append";
append(l, 6);
print l; // [1, 2, 3, 4, 5, 6];

print "Insert";
insert(l, 0, -1);
print l; // [-1, 1, 2, 3, 4, 5, 6];

print "Pop";
print pop(l); // 6

print "Delete";
delete(l, 0);
print l; // [1, 2, 3, 4, 5];

fun reverse(l) {
    var n = len(l); // also works on strings

    for (var i = 0; i < n / 2; i = i + 1) {
        var tmp = l[i];
        l[i] = l[n - 1 - i];
        l[n - 1 - i] = tmp;
    }
}

print "Reversed";
reverse(l);
print l; // [5, 4, 3, 2, 1];

var x = list(0, 5); 
print x; // [0, 0, 0, 0, 0]
x[1] = "hello";
x[2] = reverse;
x[3] = "world";
print x; // [0, hello, <fn reverse>, world, 0]
x[2](x); // [0, world, <fn reverse>, hello, 0]
print x;

var fib = [0, 1]; 
for (var i=0; i<15; i=i+1) append(fib, fib[-1] + fib[-2]);

print "Fibonacci numbers";
print fib; // [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987]

Note

• You can use the Odin compiler's -o:speed flag for better performance.
• You can use NaN boxing for better cache locality. Tested only on x86_64.

odin run loxi -o:speed -define:NAN_BOXING=true -- eg/fib.lox 

Build and run

# repl
odin run loxi

# file
odin run loxi -- <filepath>

Build

# repl
odin build loxi

# file
odin build loxi 

Run

# repl
./loxi.bin

# file
./loxi.bin <filepath>

Debug flags

# repl
odin run loxi -define:PRINT_CODE=true -define:TRACE_EXECUTION=true -define:LOG_GC=true

# file
odin run loxi -define:PRINT_CODE=true -define:TRACE_EXECUTION=true -define:LOG_GC=true -- <filepath>

WASM

git switch wasm
odin build ./loxi -target:js_wasm32 -out:./docs/loxi.wasm -no-entry-point -o:speed
miniserve ./docs --index ./docs/index.html