apg-js-examples/src/look-ahead/not.js

Examples of using the suite of apg-js applications and libraries.

/*  *************************************************************************************
 *   copyright: Copyright (c) 2021 Lowell D. Thomas, all rights reserved
 *     license: BSD-2-Clause (https://opensource.org/licenses/BSD-2-Clause)
 *   ********************************************************************************* */
// Demonstration for the `NOT(!)` syntactic predicate operator.
// This is a grammar for the C-style comment.
// The problem is that after the initial "/\*", we want to collect all characters,
// including  "\*" and "/" characters up until they appear in the
// specific combination "\*/"
// This is easily done with a `NOT` operator.
//
// Here we have separated the end characters "\*/" and the stop characters (also "\*/")
// into to differently named rules. This example will demonstrate that the
// stop rule does not appear on the `AST` even though specifically named to it.
(function not() {
  const setup = require('./setup');
  const grammar = new (require('./c-comment'))();
  const input = '/* a comment with **** characters, line breaks \n and \r\n and tabs \t ****/';
  console.log(`the grammar:`);
  console.log(grammar.toString());
  console.log(`the input string:`);
  console.log(input);
  const callbacks = [];
  callbacks.any = false;
  callbacks.begin = true;
  callbacks.comment = true;
  callbacks.end = true;
  callbacks.stop = true;
  setup(grammar, callbacks, input);
})();