/**
  * @param string $stringExpression
  * @return float
  * @throws InvalidExpressionException
  */
 public function evaluate($stringExpression)
 {
     $infixArray = $this->expressionParser->parse($stringExpression);
     $rpnExpression = $this->notationTransformer->infixToRpn($infixArray);
     $result = $this->evaluateRpnExpression($rpnExpression);
     return $result;
 }
 /**
  * @expectedException \SimpleCalculator\Exception\InvalidOperator
  */
 public function test_it_throws_InvalidOperator_exception_for_expression_with_unknown_operator()
 {
     $this->notationTransformer->infixToRpn(['1', '#', '2', '*', '3']);
 }