/* *************************************************************************************
* copyright: Copyright (c) 2021 Lowell D. Thomas, all rights reserved
* license: BSD-2-Clause (https://opensource.org/licenses/BSD-2-Clause)
* ********************************************************************************* */This is a demonstration of the look ahead operators &(AND) and !(NOT)
module.exports = function main(args) {
/* display the program arguments */
console.log('look-ahead args');
console.dir(args);
/* the help screen */
let desc = '';
desc += 'The "look-ahead" example demonstrates the use of the look ahead operators,\n';
desc += '&(AND) and !(NOT).\n';
desc += 'Examine or run a debugger on this module, "apg-js-examples/src/look-ahead/main.js" to study the example.\n';
let help = '';
help += 'Usage: npm run look-ahead [-- arg]\n';
help += ' arg: help (or no arg) to display this help screen.\n';
help += ' and demonstrate the & operator\n';
help += ' not demonstrate the ! operator\n';
help += ' compound demonstrate nested look ahead operators\n';
help += ' all run all demonstrations\n';
if (!args[0]) {
/* display the help screen and exit */
console.log(desc);
console.log(help);
return;
}
switch (args[0]) {
case 'help':
console.log(help);
return;
case 'and':
require('./and');
break;
case 'not':
require('./not');
break;
case 'compound':
require('./compound');
break;
case 'all':
require('./and');
require('./not');
require('./compound');
break;
default:
console.log(`unrecognized argument: ${args[0]}`);
console.log(help);
}
};