calculator.ast.php.js

calculator.ast.php.js

/**
 * Calculator grammar for a parser in Python.
 *
 * syntax-cli -g calculator.ast.php.js -m LALR1 -o CalcParser.php
 *
 * <?php
 *
 *   require('CalcParser.php');
 *   var_dump(CalcParser::parse('2 + 2 * 2'));
 */

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

  "moduleInclude": `
    // Can be "require" statments, or direct declarations.

    class Node {
      public function __construct($type) {
        $this->type = $type;
      }
    }

    class BinaryExpression extends Node {
      public function __construct($left, $right, $op) {
        parent::__construct('Binary');
        $this->left = $left;
        $this->right = $right;
        $this->op = $op;
      }
    }

    class PrimaryExpression extends Node {
      public function __construct($value) {
        parent::__construct('Primary');
        $this->value = intval($value);
      }
    }

    // Standard hook on parse beging, and end:

    yyparse::setOnParseBegin(function($string) {
      var_dump('Custom hook on parse begin. Parsing:', $string);
    });

    yyparse::setOnParseEnd(function($value) {
      var_dump('Custom hook on parse end. Parsed:', $value);
    });
  `,

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

  "bnf": {
    "E": [
      ["E + E",  "$$ = new BinaryExpression($1, $3, $2)"],
      ["E * E",  "$$ = new BinaryExpression($1, $3, $2)"],
      ["NUMBER", "$$ = new PrimaryExpression($1)"],
      ["( E )",  "$$ = $1"],
    ],
  },
}