Dart-specific parser generator.

calculator.txt

options {
  prefix: 'MyAmazingCalculatorGrammar',
  mixins: {
    ExampleMixin: 'example_mixin.dart'
  }
}

lexer {
  // Tags for grouping tokens separately, i.e. comments
  
  #comment {
    '//' (!'\n')*
  }

  #skip => /[ \r\n\t]+/;
  
  LPAREN => '[';
  RPAREN => ']';
  CARET => '^';
  PLUS => '+';
  MINUS => '-';
  TIMES => '*';
  SLASH => '/';
  EQUALS => '=';
  
  NUMBER => '-'? /[0-9]+/ ('.' /[0-9]+/)?;
}

parser {
  Expr(int pr) {
    :LiteralExpr() => NUMBER;
    :ParenthesisExpr() => LPAREN Expr RPAREN;
    :ExponentialExpr() if <pr >= 1> => Expr<0> #left CARET Expr<0>#right;
    :MultiplicationExpr() if <pr >= 2> => Expr<0> #left TIMES Expr<0>#right;
    :DivisionExpr() if <pr >= 3> => Expr<0> #left SLASH Expr<0>#right;
    :AdditionExpr() if <pr >= 4> => Expr<0> #left PLUS Expr<0>#right;
    :SubtractionExpr() if <pr >= 5> => Expr<0> #left MINUS Expr<0>#right;
  }
}

example_mixin.dart

class ExampleMixin {
  void foo() => print('Hello, world!');
}

main.dart

main(List<String> args) async {
  var lexer = new MyAmazingCalculatorGrammarLexer();
  var parser = new MyAmazingCalculatorGrammarParser();
  
  if (args.isEmpty) {
    // ...
  }
  
  // Will work asynchronously :)
  await new File(args.first).openRead().transform(lexer).pipe(parser);
  
  // Streaming parser to siphon events
  
  parser.onExpr.first.then((expr) {
    if (expr is MultiplicationExpr) {
      // ...
    }
  });
}