public static void TestExpression(string expression, int expectedResult)
{
/*
* this function tests the evaluate function for the Expression Parser.
* It takes a string literal of the expression, evaluates it, and then compares
* it to the same expression (in integer form) solved by the compiler
*/
Console.WriteLine("Testing Expression Parser for the equation: " + expression);
ExpressionTree parserTestTree = ExpressionParser.CreateTree(expression);
int treeResult = parserTestTree.Evaluate();
Console.WriteLine("Evaluated Expression: " + treeResult);
Console.WriteLine("Expected Result: " + expectedResult);
Debug.Assert(treeResult == expectedResult);
Console.WriteLine();
}
public static ExpressionTree CreateTree(string formula)
{
ExpressionTree tree = new ExpressionTree();
string[] formulaArray = formula.Split();
int n, currentOperationNum = -1, previousOperationNum = -1;
Node <string> leftChildOperand, rightChildOperand, parentOperator;
Stack <Node <string> > operands = new Stack <Node <string> >();
Stack <Node <string> > operators = new Stack <Node <string> >();
for (int i = 0; i < formulaArray.Length; i++)
{
Node <string> newNode = new Node <string> {
Value = formulaArray[i], leftChild = null, rightChild = null
};
if (int.TryParse(newNode.Value, out n)) // tests if the node's value is an integer or not
{
operands.Push(newNode);
}
else
{
switch (newNode.Value)
{
case "+":
currentOperationNum = 0;
break;
case "-":
currentOperationNum = 1;
break;
case "*":
currentOperationNum = 2;
break;
case "/":
currentOperationNum = 3;
break;
case "^":
currentOperationNum = 4;
break;
}
if (previousOperationNum == -1)
{
previousOperationNum = currentOperationNum;
}
else if (currentOperationNum <= previousOperationNum)
{
rightChildOperand = operands.Pop();
leftChildOperand = operands.Pop();
parentOperator = operators.Pop();
parentOperator.rightChild = rightChildOperand;
parentOperator.leftChild = leftChildOperand;
operands.Push(parentOperator);
}
previousOperationNum = currentOperationNum;
operators.Push(newNode);
}
}
while (operators.Count > 0)
{
rightChildOperand = operands.Pop();
leftChildOperand = operands.Pop();
parentOperator = operators.Pop();
parentOperator.rightChild = rightChildOperand;
parentOperator.leftChild = leftChildOperand;
operands.Push(parentOperator);
}
tree.rootNode = operands.Pop();
return(tree);
}
