grammar.js

const regexp = {
  signPrefix: /([+-][,_]*)/,
  intUnsigned:
    /(\d[,_\d]*|0[,_]*([xX][,_0-9A-Fa-f]+|[bB][,_01]+|[oO][,_0-7]+))/,
  floatUnsigned:
    /(NaN|Inf|(\d[,_\d]*(\.[,_\d]*)?|\.[,_]*\d[,_\d]*)([eE][,_]*[+-]?[,_]*\d[\d,_]*)?)/,
  symbolChar: /[^()\[\]{};"'`~\s.]/,
};

module.exports = grammar({
  name: "hy",
  rules: {
    source_file: ($) => seq(optional($.shebang), repeat($._element)),
    shebang: () => /#!.*/,

    _element: ($) => choice($.comment, $._form),

    _form: ($) => choice($._identifier, $._sequence, $._string),
    _sequence: ($) => choice($.expression, $.list),

    expression: ($) => seq("(", repeat1($._element), ")"),
    list: ($) => seq("[", repeat($._element), "]"),

    _identifier: ($) =>
      choice($._numeric_literal, $.dotted_identifier, $.keyword, $.symbol),

    _numeric_literal: ($) => choice($.int, $.complex, $.float),
    int: () => token(seq(optional(regexp.signPrefix), regexp.intUnsigned)),
    float: () => token(seq(optional(regexp.signPrefix), regexp.floatUnsigned)),
    complex: () =>
      token(
        seq(
          optional(
            seq(
              optional(regexp.signPrefix),
              regexp.floatUnsigned,
              regexp.signPrefix,
            ),
          ),
          regexp.floatUnsigned,
          /[jJ]/,
        ),
      ),

    dotted_identifier: ($) =>
      choice(
        seq(
          token("."),
          repeat(token.immediate(".")),
          $._symbol_immediate,
          repeat(seq(token.immediate("."), $._symbol_immediate)),
        ),
        seq($.symbol, repeat1(seq(token.immediate("."), $._symbol_immediate))),
      ),

    keyword: () => token(seq(":", repeat(regexp.symbolChar))),
    symbol: () => token(repeat1(regexp.symbolChar)),
    _symbol_immediate: ($) =>
      alias(token.immediate(repeat1(regexp.symbolChar)), $.symbol),

    _string: ($) => choice($.string),
    string: () => /"[^"]*"/,

    comment: () => /;.*/,
  },
});