public bool CanAddValue()
{
//value input after another value, unary operators or right parenthesis is not allowed
var invalidTypes = new HashSet <KeyType>()
{
KeyType.Value,
KeyType.Unary,
KeyType.Right
};
return(!invalidTypes.Contains(KeyHistory.Last()));
}
private void AddLeftParenthesis(string input)
{
//left parenthesis cannot immediately follow a value or unary operator
if (KeyHistory.Last() == KeyType.Value || KeyHistory.Last() == KeyType.Unary)
{
throw new InvalidOperationException("Missing Operators.");
}
//left parenthesis cannot immediately follow right parenthesis
if (KeyHistory.Last() == KeyType.Right)
{
throw new InvalidOperationException("Mismatched Parentheses.");
}
Buffer.Add(input);
KeyHistory.Add(KeyType.Left);
}
public void AddBinary(string input)
{
//consecutive binary operator input is not allowed
if (KeyHistory.Last() == KeyType.Binary)
{
throw new InvalidOperationException("Missing Operand.");
}
/*
* when binary operator input follows left parenthesis or nothing,
* a value of zero will be added as default operand
*/
if (KeyHistory.Last() == KeyType.Left || KeyHistory.Last() == KeyType.Empty)
{
AddValue(0);
}
Buffer.Add(input);
KeyHistory.Add(KeyType.Binary);
}
private void AddRightParenthesis(string input)
{
//right parenthesis cannot immediately follow binary operator
if (KeyHistory.Last() == KeyType.Binary)
{
throw new InvalidOperationException("Missing Operand.");
}
//parentheses must match
if (MissingParentheses(Expression) < 1)
{
throw new InvalidOperationException("Mismatched Parentheses.");
}
if (KeyHistory.Last() == KeyType.Left)
{
AddValue(0);
}
Buffer.Add(input);
KeyHistory.Add(KeyType.Right);
}