GLOX

The goal of this project was to create a simple programming language and learn about bytecode-compiler/virtual-machine. It is heavily inspired by Robert Nystrom's book "crafting interpreters" and implements features from chapter 14 to 24. But I've made a few changes, which are listed below.

changes

• there are two type of numbers float64 and int64
• few keywords are different var is let and fun is fn
• new variable can't be declared without an initial value

   let num = 5; 

• Assign(=) is not an operator, it's a statement
• operator precedence order is copied from Golang
• supports all the prefix(~, +, -) and infix(+, -, *, /, %, &, |, ^, <<, >>, ==, !=, <, <=, >, >=, ||, &&) operators
• supports all the Op= type statements like +=, -=, *=, /= etc.
• {} after if cond and while cond is must, similar to Golang and parenthesis around cond is not necessary

if 1<2 {
    print "true";
} else {
    print "false";
}

• print statement can take multiple arguments print "hello", "world";
• no support for for loop because while can do it all
• added support for break statement
• doesn't follow the exact same implementation details from the book
• no support for string interning
• no jump in logical expressions

sample code

fn fact(n) {
    if n <= 1 {
        return 1;
    }
    return n * fact(n-1);
}

let n = 6;
print "factorial of", n, "is", fact(n);

let i = 0;
let sm = 0;
while i <= 1_000_000 {
    i += 1;
    sm += i;
}
print sm;

try it out

$ git clone https://github.com/2asm/glox
$ cd glox
$ go build .
$ ./glox test.glox

Useful resources

https://craftinginterpreters.com/
https://interpreterbook.com/
https://matklad.github.io/2020/04/13/simple-but-powerful-pratt-parsing.html
https://en.wikipedia.org/wiki/Operator-precedence_parser
https://github.com/golang/go/tree/master/src/go