private static OpItem isOperator(int i, string expression, string[] operators)
{
OpItem op_item = null;
string substrOfExpression = expression.Substring(i);
foreach (string opItemValue in operators)
{
if (substrOfExpression.StartsWith(opItemValue))
{
op_item = new OpItem(i += opItemValue.Length - 1, opItemValue);
break;
}
}
return op_item;
}
/**
* @parameter input - string, comes from user input
* from calculator app
**/
public List<string> parseInputToInfix(string input)
{
List<string> inputItems = new List<string>();
//list of registered operators
//operators are already registered in CalculationController
Dictionary<string, IGeneralOperator> operatorKeyValue = this.typeMan.typesList;
//sort opereators' by their value length
string[] operators = getSortedOperators(operatorKeyValue);
//remove white spaces from input expression
string expression = Regex.Replace(input, @"\s+", "");
//helps to collect operands
StringBuilder sb = new StringBuilder();
//for detecting consequtive operators
string prevItem = "";
//loop over input
for (int i = 0; i < expression.Length; i++)
{
OpItem isOpera = isOperator(i, expression, operators);
//operators
if (isOpera != null)//an operator is encountered
{
/////////////////////////////////
//OPERATOR ...
string currentOperator = isOpera.opValue;
/////////////////////////////////
//OPERAND
//we encoutered an operator, so add collected operands to stack
if (sb.Length > 0)//dont add empty sb
{
//store operand
prevItem = sb.ToString();
inputItems.Add(prevItem);
//init new operand collector
sb = new StringBuilder();
}
else
{
//if previous item was also operator, add operand 0
//but allow multiple parenthesis
if (currentOperator != "(" && currentOperator != ")")
if (prevItem != "(" && prevItem != ")")
inputItems.Add("0");
}
/////////////////////////////////
//... OPERATOR continues
//add operator to the list
inputItems.Add(currentOperator);
//increment index i to continue looping after current operator
i = isOpera.index;
//store operator
prevItem = currentOperator;
}
//collect operands into stringbuilder sb
else
{
sb.Append(expression[i]);
}
}
//remaining operand at the end of an input string
if (sb.Length > 0)
{
inputItems.Add(sb.ToString());
}
return inputItems;
}