How to implement assignment operator (=)?

[martinjo]

I'm trying (desperatly 😢) to implement an assignment operator. I'd like to be able to update my context with the result of expressions.

This is what I have:

binary('=', 0);
operator('=', (left: any, right: any) => (ctx: any) => {
    // Make sure the left side is a variable reference
    if (typeof left !== 'string') {
        throw new Error('Left side of assignment must be a variable name');
    }

    // Evaluate the right side in the context
    right = compile(right);
    const value = right(ctx);
    // Assign the value in the context
    ctx[left] = value;
    // Return the value
    return value;
});

It works for simple expressions like contextVar = anotherContextVar

But as soon as I use a more complicated expression like contextVar = anotherContextVar + 2 it fails since my right varible will get an array of values 🤷‍♂️. I feel I'm making a simple mistake here, but I can't seem to figure it out. Any suggestions?

[dy]

I've fixed some mistakes in the readme. Here's the example you need: https://github.com/dy/subscript/blob/main/test/subscript.js#L447-L457 Please lmk if it works.

[dy]

Ok, I hope it helped. Thanks for the issue, please reopen if it doesn't work.

[martinjo]

Thanks so much for the help! I'll soon get around to try it :)

[martinjo]

When I try the code you link to with the following simple statement: 'localvar = 0' I get the following error:

TypeError: cur.charCodeAt is not a function at parse.space (parse.js:58:48) at expr (parse.js:34:16) at parse (parse.js:7:33) at subscript (subscript.js:8:27) at interpreter.ts:197:22 at operators. [as =] (compile.js:6:73) at compile (compile.js:2:95) at subscript.js:8:56 at evalSubscript (interpreter.ts:188:34) at evalCode (interpreter.ts:50:17)

I can see my function for '=' getting called with a = 'localvar' b = '["",0]' (using JSON.stringify(b))  What am I missing?

[dy]

There's something you do wrong. Please check this code, it works:

import subscript, { operator, binary, compile } from 'subscript.js'

  binary('=', 10, true)
  operator('=', (a, b) => {
    const calc = compile(b);
    return ctx => (ctx[a] = calc(ctx))
  })

  const fn = subscript('localvar = 0')
  let state = {}
  fn(state)
  state.localvar === 0 //true