/**
* Try calculating the current expression
* @returns current expression (calculated) or "ERROR" string if something went wrong
*/
public string Result()
{
string result = "";
try
{
// Explicitly handle factorials because `Evaluate` method has no operand for them.
string parsed_result = EvaluateUnknownFactorials(this.ExpressionCurrent);
result = CalculatorLogic.Evaluate(parsed_result).ToString();
this.ExpressionCurrent = result;
}
catch (Exception)
{
this.ClearCurrent();
result = "ERROR";
}
// By returning the result and cleaning the inner memory is how we
// achieve the lazy displaying of the result while still "clearing"
// the screen once new numbers get pressed
//this.ClearCurrent();
return(result);
}
public MainWindow()
{
InitializeComponent();
this.calculatorLogic = new CalculatorLogic();
// Bind the display widgets to the appropriate handler
this.display = new DisplayLogic(textDisplayPrevious, textDisplayExpression, textDisplayResult);
}
/**
* Find every factorial in a substring and evaluate it. Works recursevly.
* Once the factorial has been evaluated -> replace the expression in
* the input string with the calculated value, return the altered string.
*
* @returns Expression where all factorials have been evaluted
*/
private static string EvaluateUnknownFactorials(string expression)
{
Match match = FACTORTIAL_TOKEN.Match(expression);
CaptureCollection captures = match.Captures;
foreach (Capture capture in captures)
{
// remove the '!' with the substring
// Perform recursive check for other factorials
string group_substring = EvaluateUnknownFactorials(capture.Value.Substring(0, capture.Value.Length - 1));
long localResult = (long)CalculatorLogic.Evaluate(group_substring);
long localResultFact = CalculatorLogic.Factorial(localResult);
expression = DirtyReplace(expression, localResultFact.ToString(), capture.Value, capture.Index);
}
// Sanity check for making sure that no factorials are left. The need for this extra check can be
// eliminated if unittests are created to prove that such construction has no need
return(expression.Contains("!") ? EvaluateUnknownFactorials(expression) : expression);
}
