Wuttyi Lang LL parsing

Environment.js

export default class Environment {

    // create a variable environment (table of environment)
    constructor(record = {}) {
        this.record = record;
    }

    // set the variable to the env with the given name and value
    define(name, value) {
        this.record[name] = value;
        return value;
    }

    // get the variable value from record
    lookup(name) {
        if (!this.record.hasOwnProperty(name)) {
            throw new ReferenceError(`ReferenceError: ${name} is not defined`)
        }
        return this.record[name];
    }
}

Wuttyi.js

import assert from 'assert';
import Environment from "./Environment.js";


/* It evaluates a JavaScript expression and returns the result */
class Wuttyi {
    // Create the Wuttyi instance with the global environment
    constructor(env = new Environment()) {
        this.global = env;
    }

    // -------------------- Self evaluation -------------
    // Evaluate an expression in the given environment
    eval(exp, env = this.global) {
        if (isNumber(exp)) {
            return exp;
        }

        if (isString(exp)) {
            return exp.slice(1, -1)
        }

        // -------------- Math Operations ---------------
        if (exp[0] === '+') {
            return this.eval(exp[1]) + this.eval(exp[2]);
        }

        if (exp[0] === '-') {
            return this.eval(exp[1]) - this.eval(exp[2]);
        }

        if (exp[0] === '*') {
            return this.eval(exp[1]) * this.eval(exp[2]);
        }

        if (exp[0] === '/') {
            return this.eval(exp[1]) / this.eval(exp[2]);
        }

        if (exp[0] === '%') {
            return this.eval(exp[1]) % this.eval(exp[2]);
        }

        // ----------------- Variable declaration ---------------
        if (exp[0] === 'var') {
            const [_, name, value] = exp;
            return env.define(name, this.eval(value));
        }

        // ---------------- Variable Access ---------------------------
        if (isVariableName(exp[0])) {
            return env.lookup(exp);
        }

        throw `Unimplemented: ${exp.stringify()}`;
    }
}


function isNumber(exp) {
    return typeof exp === 'number';
}

function isString(exp) {
    return typeof exp === 'string' && exp.startsWith('"') && exp.endsWith('"');
}

function isVariableName(exp) {
    return typeof exp === 'string' && /^[a-zA-Z][a-zA-Z0-9_]*$/.test(exp);
}

// -------------------- Tests ----------------
// set the predefined variable
const wuttyi = new Wuttyi(new Environment({
    true: true,
    false: false,
    null: null,
    version: '1.0.0',
}));

// ----------- Math Tests ----------------------
// exp ::= number | string | [+ number, number]
assert.strictEqual(wuttyi.eval(1), 1);
assert.strictEqual(wuttyi.eval('"hello"'), 'hello');
assert.strictEqual(wuttyi.eval(['+', 1, 2]), 3);
assert.strictEqual(wuttyi.eval(['+', ['+', 6, 2], 2]), 10);
assert.strictEqual(wuttyi.eval(['+', ['*', 6, 2], 2]), 14);
assert.strictEqual(wuttyi.eval(['*', ['+', 2, 3], 5]), 25);

// ------------- Variable -----------------------
assert.strictEqual(wuttyi.eval(['var', 'x', 10]), 10);
assert.strictEqual(wuttyi.eval('x'), 10);

// var isUser = true;
assert.strictEqual(wuttyi.eval(['var', 'isUser', 'true']), true);
assert.strictEqual(wuttyi.eval('isUser'), true);

assert.strictEqual(wuttyi.eval(['var', 'y', 100]), 100);
assert.strictEqual(wuttyi.eval('y'), 100);


console.log('Asserting was passed')