//build the tree (bottom up) using the shuntingYard stacks
private bool buildTree()
{
//pop operators from stack -> build tree
//OpNode temp;
// if (root.operationType == '_')
// {
root = operators.Pop();
root.right = operands.Pop();
root.left = operands.Pop(); //after building tree,
operands.Push(new ValNode(root.Eval())); //evaluate, and push value to output
return(true);
//return true;
// }
//else
//{
// temp = root; //hold sub-tree
// //operands.Pop(); //pop the result -- right sub-tree == result
// root = operators.Pop(); //grab an operator
// root.right = temp; //restore sub-tree, making right-heavy tree
// root.left = operands.Pop(); //if we don't push the result (leave it in tree) this works
// return true;
//}
//int valCount = eTokens.Length; //keep #items handy
//int leafVal = 0; //out variable -- required for parsing
}
// Created this method to prevent bloat in code
private Node formTree(Stack <Node> operands, Stack <OpNode> operators)
{
// While there are no OpNode on the operatorsStack, form appropriate branches and place in operands stack
while (operators.Count > 0)
{
OpNode newParent = operators.Pop();
newParent.RightChild = operands.Pop();
newParent.LeftChild = operands.Pop();
root = newParent;
operandStack.Push(newParent);
}
return(root);
}
private double Eval(Node node)
{
//Evaluate based on the kind of node
ConstNode constnode = node as ConstNode;
if (constnode != null)
{
return(constnode.OpValue);
}
VarNode varnode = node as VarNode;
if (varnode != null)
{
try
{ return(variableDict[varnode.Name]); }
catch
{
Console.WriteLine("Variable " + varnode.Name + " has not been defined. Continuing evaluation with variable equal to 0.");
}
}
OpNode opnode = node as OpNode;
if (opnode != null)
{
switch (opnode.Op)
{
case '+':
return(Eval(opnode.Left) + Eval(opnode.Right));
case '-':
return(Eval(opnode.Left) - Eval(opnode.Right));
case '*':
return(Eval(opnode.Left) * Eval(opnode.Right));
case '/':
return(Eval(opnode.Left) / Eval(opnode.Right));
}
}
return(0);
}
// Factory for ExpNodes to create an expression tree.
protected ExpNode ConstructTreeFromTokens(List <string> expressionInPostfixNotation)
{
Stack <ExpNode> stack = new Stack <ExpNode>();
foreach (string tok in expressionInPostfixNotation)
{
if (operators.TryGetValue(tok, out OperatorToken op)) //if the token is an operator
{
ExpNode newrightNode = stack.Pop(); //grabs the right and left nodes from the stack
ExpNode newLeftNode = stack.Pop();
ExpNode newOpNode = new OpNode(ref newLeftNode, ref newrightNode, op.Symbol[0]); // Creates an OpNode with the nodes we just popped off the stack.
stack.Push(newOpNode); // Adds the new operator node to the stack.
}
else // if the token is an operand
{
stack.Push(MakeDataNode(tok)); //push the operand node on to the stack
}
} //when there are no more tokens. There should only be one node on the stack.
return(stack.Pop()); // returns the root node of the tree.
}
private double Eval(Node node)
{
//Evaluate based on the kind of node
ConstNode constnode = node as ConstNode;
if (constnode != null)
{
return(constnode.OpValue);
}
VarNode varnode = node as VarNode;
if (varnode != null)
{
// used to be a try/catch, but now we set every new variable to 0 when the tree is made, so there will always be a value to obtain.
return(variableDict[varnode.Name]);
}
OpNode opnode = node as OpNode;
if (opnode != null)
{
switch (opnode.Op)
{
case '+':
return(Eval(opnode.Left) + Eval(opnode.Right));
case '-':
return(Eval(opnode.Left) - Eval(opnode.Right));
case '*':
return(Eval(opnode.Left) * Eval(opnode.Right));
case '/':
return(Eval(opnode.Left) / Eval(opnode.Right));
}
}
return(0);
}
} //allow tree to tell its current expression
//Expression Tree Constructor
//--builds ExpTree according to given expression, with default expression if never supplied one
public ExpTree(Cell c, Cell[][] spc, string expression = "4+18/(9-3)")
{
root = new OpNode('_'); //'_' == special marker for base tree-building case
currentExpression = expression; //hold the expression -- allows re-parsing -- not needed once I build the tree for real?
variables = new Dictionary <string, double>(); //create new dictionary for variableName:value mapping
operands = new Stack <Node>(); //shuntingYard Operand Stack
operators = new Stack <OpNode>(); //shuntingYard Operator Stack
//output = new Stack<Node>(); //shuntingYard Output Stack
precedence = new Dictionary <string, int>() //shuntingYard Precedence Mapping
{
{ "(", 0 }, { ")", 3 }, { "*", 2 }, { "/", 2 }, { "+", 1 }, { "-", 1 }
};
evalResult = -42.0; //make initial value an uncommon result
expressionTokens = parseExp(ref c, ref spc, currentExpression); //use self-made parser, couldn't get my RegEx right..
if (expressionTokens[0] == "" || isOperator(expressionTokens[0]))
{
c.Text = "#REF!";
c.bgColor = "Red";
c.clearRefDict(); //clear refs so it can re-evaluate
}
//shuntYard(expressionTokens); //convert to RPN & build tree with Shunting Yard Algorithm
}
// recursive function to set a variable node.
protected void SetVarNode(ref VarNode input, OpNode node)
{
if (VariableNodeCompare(input, node.left)) //if the left node is a Variable node and has the same variable name
{
(node.left as VarNode).Value = input.Value;
}
else if (VariableNodeCompare(input, node.right)) //if the right node is a Variable node and has the same variable name
{
(node.right as VarNode).Value = input.Value;
}
else
{
if (node.right as OpNode != null) //if the right side node is an operator node
{
SetVarNode(ref input, node.right as OpNode); //check right subtree
}
if (node.left as OpNode != null) //if the right side node is an operator node
{
SetVarNode(ref input, node.left as OpNode); //check right subtree
}
}
}
public ExpTree(string expression)
{
Stack <string> equationStack = new Stack <string>();
Stack <string> treeStack = new Stack <string>();
Stack <Node> buildTree = new Stack <Node>();
string tempString = "";
//format expression to work with parser
expression = "(" + expression + ")";
char[] tokens = expression.ToCharArray();
//build stack from parsed expression - shunting yard algorithm
for (int i = 0; i < tokens.Length; i++)
{
if (tokens[i] == '(')
{
equationStack.Push(tokens[i].ToString());
}
else if (tokens[i] == ')') // doesn't push ")" to equation stack
{
while (equationStack.Peek() != "(") // pop until lhs bracket is found
{
treeStack.Push(equationStack.Pop()); // add right child and operator
}
equationStack.Pop(); // get rid of "("
}
else if (operators.Contains(tokens[i].ToString())) // current token is an operator
{
while (equationStack.Peek() != "(" &&
(!operators.Contains(equationStack.Peek()) ||
(getPrecedence(tokens[i].ToString()) < getPrecedence(equationStack.Peek())) || /*check if stack top is operator of higher precedence*/
(getPrecedence(tokens[i].ToString()) == getPrecedence(equationStack.Peek()))))
{
treeStack.Push(equationStack.Pop());
}
equationStack.Push(tokens[i].ToString());
}
else // integer or variable
{
// get numbers with multiple digits (will always execute at least once)
while (tokens[i] != '(' && tokens[i] != ')' && !operators.Contains(tokens[i].ToString()))
{
tempString += tokens[i];
i++;
}
if (tokens[i] == '(' || tokens[i] == ')' || operators.Contains(tokens[i].ToString()))
{
i--; //move back so token isn't skipped in next iteration
}
equationStack.Push(tempString);
tempString = "";
}
}
equationStack.Clear();
//reverse stack to get postfix expression
while (treeStack.Count != 0)
{
equationStack.Push(treeStack.Pop());
}
//build tree
while (equationStack.Count != 0) //equationStack now contains postfix expression
{
tempString = equationStack.Pop();
if (operators.Contains(tempString)) //make opNode
{
OpNode newNode = new OpNode(tempString);
if (buildTree.Count >= 2)
{
newNode.right = buildTree.Pop();
newNode.left = buildTree.Pop();
buildTree.Push(newNode);
}
}
else
{
if (tempString.All(Char.IsDigit)) //make valNode
{
ValNode newNode = new ValNode(tempString);
buildTree.Push(newNode);
}
else //make varNode
{
char let = Char.ToUpper(tempString[0]);
string row = tempString.Substring(1);
tempString = let + row;
if (!varDict.ContainsKey(tempString))
{
varDict[tempString] = 0; //initialize all variables to 0
}
VarNode newNode = new VarNode(tempString);
buildTree.Push(newNode);
varList.Add(tempString); //add to list of cell references
}
}
}
this.root = buildTree.Pop(); //final item in stack will be root node pointing to subtrees
}
private string userInput; // Used for menu interface
public ExpTree(string expression)
{
int operandBegin = 0; // Index of where the first character of the operand exists
bool exit = false; // Used for logic with paranthesis and how they are placed onto appropriate stack
bool paranthesis = false; // If true, we know that the last paranthesis was placed onto stack and we do not need to create another operand for current operator
// Iterate through length of given expression
for (int i = 0; i < expression.Length; i++)
{
char currentChar = expression[i];
// If looking at an operator
if (currentChar == '+' || currentChar == '-' || currentChar == '*' || currentChar == '/')
{
// Create an appropriate OpNode
OpNode newOp = new OpNode(currentChar.ToString());
// Last thing we looked at was not ')'
if (paranthesis == false)
{
// Create an operand node with last operand and place onto stack
Node newNode = determineNode(expression, operandBegin, i);
operandStack.Push(newNode);
}
// We know that there is no 'new' operand to be placed on stack, sub-tree contained in () is already placed onto operand stack
else
{
// Reset the paranthesis flag
paranthesis = false;
}
// Next operand should begin immediately after the operator, note this would be different if urnary operators were included
operandBegin = i + 1;
// Determine what to do with current and previous operators
if (operatorStack.Count > 0)
{
// Need to peak at top of operand stack, if higher precedence need to push current operand down
if (operatorStack.Peek().Precedence < newOp.Precedence)
{
operatorStack.Push(newOp);
}
// If lower precedence, need to pop and form node
else
{
OpNode newParent = operatorStack.Pop();
newParent.RightChild = operandStack.Pop();
newParent.LeftChild = operandStack.Pop();
operandStack.Push(newParent);
operatorStack.Push(newOp);
}
}
else
{
// If the operator stack is empty, it is essentially a sentinal like the hint paper was describing
operatorStack.Push(newOp);
}
}
else if (currentChar == '(')
{
// Need to form new tree
ExpTree newTree = new ExpTree(expression.Substring(i + 1));
//TEST
i = expression.IndexOf(')', i + 1);
paranthesis = true;
operandStack.Push(newTree.root);
}
else if (currentChar == ')')
{
// End new tree, pop back out
Node newNode = determineNode(expression, operandBegin, i);
operandStack.Push(newNode);
root = formTree(operandStack, operatorStack);
exit = true;
break;
}
}
// Since we are only using binary oprators, the operand stack must be even when expression is completely evaluated
if (operandStack.Count > 0 & (operandStack.Count % 2 != 0) & exit == false)
{
Node newNode = determineNode(expression, operandBegin, expression.Length);
operandStack.Push(newNode);
}
// Provide an entry point for outside world to access
root = formTree(operandStack, operatorStack);
}
