/**
* @return mixed
*/
public function start()
{
// Input
echo 'Formel: ';
$formula = trim(fgets(STDIN));
// Processing
$formulaObj = $this->parser->parse($formula);
$result = $this->calculator->calculate($formulaObj);
// Output
echo 'Ergebnis: ';
echo $result;
echo "\n";
}
