@thi.ng/sexpr/parse.js

Extensible S-Expression parser & runtime infrastructure

import { isString } from "@thi.ng/checks/is-string";
import { unescape } from "@thi.ng/strings/escape";
import {
  DEFAULT_SYNTAX
} from "./api.js";
import { tokenize } from "./tokenize.js";
class ParseError extends Error {
  line;
  col;
  constructor(msg, line, col) {
    super(msg);
    this.line = line;
    this.col = col;
  }
}
const parse = (src, opts) => {
  const { scopes } = { ...DEFAULT_SYNTAX, ...opts };
  const scopeOpen = scopes.map((x) => x[0]);
  const scopeClose = scopes.map((x) => x[1]);
  const tree = [{ type: "root", children: [] }];
  let currScope = -1;
  for (let token of isString(src) ? tokenize(src, opts) : src) {
    const t = token.value;
    let tmp;
    if ((tmp = scopeOpen.indexOf(t)) !== -1) {
      tree.push({ type: "expr", value: t, children: [] });
      currScope = tmp;
    } else if ((tmp = scopeClose.indexOf(t)) !== -1) {
      if (tree.length < 2 || currScope !== tmp) {
        throw new ParseError(`unmatched '${t}'`, token.line, token.col);
      }
      tree[tree.length - 2].children.push(tree.pop());
      currScope = scopeOpen.indexOf(
        tree[tree.length - 1].value
      );
    } else {
      let node;
      let value;
      if (t.startsWith('"')) {
        node = {
          type: "str",
          value: unescape(t.substring(1, t.length - 1))
        };
      } else if (t.startsWith("0x") && !isNaN(value = parseInt(t.substring(2), 16)) || !isNaN(value = parseFloat(t))) {
        node = { type: "num", value };
      } else {
        node = { type: "sym", value: t };
      }
      tree[tree.length - 1].children.push(node);
    }
  }
  if (tree.length > 1) {
    throw new ParseError("unclosed s-expression", -1, -1);
  }
  return tree[0];
};
export {
  ParseError,
  parse
};