ast is being modified by hoist

Is there a way to avoid ast modification? Because my code runs pretty slow because of multiple acorn.parse, so I created a single ast by running acorn.parse one time and run the same ast multiple times. That’s what I do in JS-Interpreter and is pretty viable as ast is not modified in any way, but keeping all the state in a different object (which I delete or recycle, depending on situations).

I like this interpreter a lot, but I’m having problems implementing it as it always need a new ast, which I create with another acorn.parse, because the ast is modified while running, so here “ast caching” is not viable. This makes this interpreter way way slower than JS-Interpreter (actually sval is way faster when interpreting the JS (about 8 times), but globally is slower if you do a lot of runs with the same code).

[Siubaak]

Yes, sval will modify ast when hoisting, but just move the function declarations to the top of the scope. No any other changes on ast except this.

After finish compile_ir branch, I will expose APIs for caching the bytecodes. Then you can just parse the code once, get the bytecodes, and run the bytecodes multiple times, like:

const interpreter = new Sval
const bytecodes = interpreter.compile('...')
interpreter.run(bytecodes) // this will skip parsing
interpreter.run(bytecodes) // this will skip parsing
interpreter.run(bytecodes) // this will skip parsing

interpreter.run('...') // you can still run code as string

[jifeon]

That’s amazing! Thank you!

I have one related question: in my project I have a case where I need to evaluate just part of ast and get result of it. run accepts Program (hoist requires it at least) and can provide output only via export. Probably you can give me an advice how can I evaluate part of code and get latest values from the stack?

Currently for MVP I used very hacked solution:

const result = sval.runAST(node).state.shift();

where runAST skips hoist. In near future I will need to rewrite it into more robust solution, so if you can give an advice it would be awesome.