Unsound lisp ast parser for RC

little-lisp.ts

function parse(str: string) {
  let index = 0;

  return walk(str);

  function walk(str: string, container: any[] = []) {
    let collect = "";
    while (index < str.length) {
      const char = str[index];

      if (char === "(") {
        next();
        const children = walk(str, []);
        container.push(children);
      } else if (char === '"') {
        const match = str.slice(index).match(/^"[^"\\]*(?:\\.[^"\\]*)*"/);
        if (match) {
          collect = "";
          container.push(match[0]);
          index += match[0].length;
          continue;
        }
      } else if (char === ")") {
        next();
        return container;
      } else if (char === " ") {
        next();
      } else {
        collect += char;
        index += 1;
      }
    }

    if (collect) container.push(collect);

    return container;

    function next() {
      if (collect && !/\r?\n+/.test(collect)) container.push(collect);
      collect = "";
      index += 1;
    }
  }
}

const ast = parse(`(map (lambda (x) (+ x 1)) (list 1 2 3 4)))`);
console.log(ast);