calculator.ast.js

calculator.ast.js

/**
 * Calculator grammar for a parser in JavaScript.
 *
 * syntax-cli -g calculator.ast.js -m LALR1 -o CalcParser.js
 *
 * const CalcParser = require('./CalcParser.js');
 * console.log(CalcParser.parse('2 + 2 * 2')); // AST
 */

{
  "lex": {
    "rules": [
      ["\\s+",  "/* skip whitespace */"],
      ["\\d+",  "return 'NUMBER'"],
      ["\\*",   "return '*'"],
      ["\\+",   "return '+'"],
      ["\\(",   "return '('"],
      ["\\)",   "return ')'"],
    ]
  },

  "operators": [
    ["left", "+"],
    ["left", "*"],
  ],

  "bnf": {
    "E": [
      ["E + E",  "$$ = {type: 'Binary', left: $1, right: $3, op: '+'}"],
      ["E * E",  "$$ = {type: 'Binary', left: $1, right: $3, op: '*'}"],
      ["NUMBER", "$$ = {type: 'Primary', value: Number($1)}"],
      ["( E )",  "$$ = $2"],
    ],
  },
}