/// <summary>
/// Converts a given postfix array to a infix expression.
/// </summary>
/// <param name="postfixExp"></param>
/// <returns></returns>
public static string Convert2Infix(string[] postfixExp)
{
Stack <string> tokenStack = new Stack <string>();
List <string> postfixList = new List <string>();
//Operator lists for different number of operands
List <string> unaryOperators = new List <string>();
List <string> binaryOperators = new List <string>();
OperatorFunctions.UnaryOperators(unaryOperators);
OperatorFunctions.BinaryOperators(binaryOperators);
//Recreate postfix list
for (int i = 0; i < postfixExp.Length; i++)
{
postfixList.Add(postfixExp[i]);
}
postfixList.Reverse();
//Iterate over all tokens in postfix expression
foreach (string token in postfixList)
{
//Binary operators
if (binaryOperators.Any(token.Contains))
{
string x = tokenStack.Pop();
string y = tokenStack.Pop();
string exp = "(" + y + token + x + ")";
tokenStack.Push(exp);
}
//Unary operators
else if (unaryOperators.Any(token.Contains))
{
string x = tokenStack.Pop();
string exp = "(" + token + "(" + x + ")" + ")";
tokenStack.Push(exp);
}
/*
* Add Numbers directly to string, the first
* one doesn't need a buffer space in-between
*/
else
{
tokenStack.Push(token);
}
}
return(tokenStack.Pop());
}
/// <summary>
/// Takes a given postfix expression and evaluates it
/// and returns the value to the main program to test
/// for convergence.
/// </summary>
/// <param name="postfixExp"></param>
/// <returns></returns>
public static double EvaluatePostFix(string postfixExp)
{
string x, y, ans;
string[] postfixArray = postfixExp.Split(null);
Stack <string> tokenStack = new Stack <string>();
//Operator lists for different number of operands
List <string> unaryOperators = new List <string>();
List <string> binaryOperators = new List <string>();
OperatorFunctions.UnaryOperators(unaryOperators);
OperatorFunctions.BinaryOperators(binaryOperators);
//Iterate over all tokens in postfix expression
foreach (string token in postfixArray)
{
if (binaryOperators.Any(token.Contains))
{
//Evaluate functions that take two arguments
y = tokenStack.Pop();
x = tokenStack.Pop();
ans = OperatorFunctions.EvaluateExp(x, y, token).ToString();
tokenStack.Push(ans);
}
else if (unaryOperators.Any(token.Contains))
{
//Evaluate functions that only take a single argument
x = "temp";
y = tokenStack.Pop();
ans = OperatorFunctions.EvaluateExp(x, y, token).ToString();
tokenStack.Push(ans);
}
else
{
tokenStack.Push(token);
}
}
//Last thing on stack is the answer
ans = tokenStack.Pop();
return(double.Parse(ans));
}
/// <summary>
/// Takes in a reverse postfix array and recursively grabs
/// an operator and two operands to be derivated such
/// that they are all complete expressions.
/// </summary>
/// <param name=""></param>
/// <returns></returns>
private static string CompleteExpressions(string[] postfixArray)
{
//Operator lists for different number of operands
List <string> unaryOperators = new List <string>();
List <string> binaryOperators = new List <string>();
OperatorFunctions.UnaryOperators(unaryOperators);
OperatorFunctions.BinaryOperators(binaryOperators);
//Initialize
int i = 0;
string token = postfixArray[0];
//Split between no, unary, and binary operators
if (unaryOperators.Any(token.Contains))
{
string A = postfixArray[1];
string B = "temp";
bool completeA = IsComplete(A);
//Loop until complete expressons
while (!completeA)
{
i++;
if (!completeA)
{
A += " " + postfixArray[i + 1];
}
//Recheck for completeness and increment
completeA = IsComplete(A);
}
string[] ArrA = A.Split(' ');
string[] ArrB = B.Split(' ');
return(EvaluateDerivative(ArrA, ArrB, token));
}
else if (binaryOperators.Any(token.Contains))
{
string B = postfixArray[1];
string A = postfixArray[2];
bool completeA = IsComplete(A);
bool completeB = IsComplete(B);
//Loop until complete expressons
while ((!completeA) || (!completeB))
{
//Try to fix completeness
if (!completeB)
{
B += " " + A;
A = postfixArray[i + 3];
}
else if (!completeA)
{
A += " " + postfixArray[i + 3];
}
//Recheck for completeness and increment
completeA = IsComplete(A);
completeB = IsComplete(B);
i++;
}
string[] ArrA = A.Split(' ');
string[] ArrB = B.Split(' ');
return(EvaluateDerivative(ArrA, ArrB, token));
}
else
{
string[] tempList = { "temp" };
return(EvaluateDerivative(tempList, postfixArray, "temp"));
}
}
