parse method

Expression parse(String inputString)

Parses the given input string into an Expression. Throws a ArgumentError if the given inputString is empty. Throws a StateError if the token stream is invalid. Returns a valid Expression.

Implementation

Expression parse(String inputString) {
  if (inputString.trim().isEmpty) {
    throw FormatException('The given input string was empty.');
  }

  final List<Expression> exprStack = <Expression>[];
  final List<Token> inputStream = lex.tokenizeToRPN(inputString);

  for (Token currToken in inputStream) {
    Expression currExpr, left, right;

    switch (currToken.type) {
      case TokenType.VAL:
        currExpr = Number(double.parse(currToken.text));
        break;
      case TokenType.VAR:
        currExpr = Variable(currToken.text);
        break;
      case TokenType.UNMINUS:
        currExpr = -exprStack.removeLast();
        break;
      case TokenType.UNPLUS:
        currExpr = UnaryPlus(exprStack.removeLast());
        break;
      case TokenType.PLUS:
        right = exprStack.removeLast();
        left = exprStack.removeLast();
        currExpr = left + right;
        break;
      case TokenType.MINUS:
        right = exprStack.removeLast();
        left = exprStack.removeLast();
        currExpr = left - right;
        break;
      case TokenType.TIMES:
        right = exprStack.removeLast();
        left = exprStack.removeLast();
        currExpr = left * right;
        break;
      case TokenType.DIV:
        right = exprStack.removeLast();
        left = exprStack.removeLast();
        currExpr = left / right;
        break;
      case TokenType.MOD:
        right = exprStack.removeLast();
        left = exprStack.removeLast();
        currExpr = left % right;
        break;
      case TokenType.POW:
        right = exprStack.removeLast();
        left = exprStack.removeLast();
        currExpr = left ^ right;
        break;
      case TokenType.EFUNC:
        currExpr = Exponential(exprStack.removeLast());
        break;
      case TokenType.LOG:
        right = exprStack.removeLast();
        left = exprStack.removeLast();
        currExpr = Log(left, right);
        break;
      case TokenType.LN:
        currExpr = Ln(exprStack.removeLast());
        break;
      case TokenType.SQRT:
        currExpr = Sqrt(exprStack.removeLast());
        break;
      case TokenType.ROOT:
        right = exprStack.removeLast();
        left = exprStack.removeLast();
        currExpr = Root.fromExpr(left as Number, right);
        break;
      case TokenType.SIN:
        currExpr = Sin(exprStack.removeLast());
        break;
      case TokenType.COS:
        currExpr = Cos(exprStack.removeLast());
        break;
      case TokenType.TAN:
        currExpr = Tan(exprStack.removeLast());
        break;
      case TokenType.ASIN:
        currExpr = Asin(exprStack.removeLast());
        break;
      case TokenType.ACOS:
        currExpr = Acos(exprStack.removeLast());
        break;
      case TokenType.ATAN:
        currExpr = Atan(exprStack.removeLast());
        break;
      case TokenType.ABS:
        currExpr = Abs(exprStack.removeLast());
        break;
      case TokenType.CEIL:
        currExpr = Ceil(exprStack.removeLast());
        break;
      case TokenType.FLOOR:
        currExpr = Floor(exprStack.removeLast());
        break;
      case TokenType.SGN:
        currExpr = Sgn(exprStack.removeLast());
        break;
      case TokenType.FACTORIAL:
        currExpr = Factorial(exprStack.removeLast());
        break;
      case TokenType.FUNC:
        List<Expression> args = [];
        for (var i = 0; i < currToken.argCount; ++i) {
          args.insert(0, exprStack.removeLast());
        }
        currExpr = AlgorithmicFunction(
            currToken.text, args, functionHandlers[currToken.text]);
        break;
      default:
        throw FormatException('Unsupported token: $currToken');
    }

    exprStack.add(currExpr);
  }

  if (exprStack.length > 1) {
    throw FormatException('The input String is not a correct expression');
  }

  return exprStack.last;
}