Node_P PlusMinus()
{
Node_P left = MultDiv();
while (true)
{
//Identify the operation
Operation op = Operation.Null;
if (splitter.current_sign == Sign.Plus)
{
op = Operation.Addition;
}
else if (splitter.current_sign == Sign.Minus)
{
op = Operation.Substraction;
}
//If no plus or minus sign is found
if (op == Operation.Null)
{
return(left);
}
splitter.Move_sign(); //move to the next sign
Node_P right = MultDiv();
//Create a node with a correspondent binary operation
left = new NodePolBinary(left, right, op);
}
}
Node_P MultDiv()
{
//Check whether the current node is a unary operator
Node_P left = Unary();
while (true)
{
//Identify the operation
Operation op = Operation.Null;
if (splitter.current_sign == Sign.Divide)
{
op = Operation.Division;
}
else if (splitter.current_sign == Sign.Multiply)
{
op = Operation.Multiplication;
}
//If no multiply or divide sign is found
if (op == Operation.Null)
{
return(left);
}
splitter.Move_sign(); //move to the next sign
//Check whether the current node is a unary operator
Node_P right = Unary();
//Create a node with a correspondent binary operation
left = new NodePolBinary(left, right, op);
}
}
Node_P Unary()
{
while (true)
{
//In case of unary plus
//Unary plus doesn't need any operation
if (splitter.current_sign == Sign.Plus)
{
splitter.Move_sign(); //Move to the next sign
continue;
}
//In case of unary minus
else if (splitter.current_sign == Sign.Minus)
{
splitter.Move_sign(); //Move to the next sign
//Recursive call to find the sequence of unary operators (if exists)
//eg -+--10 = -10
Node_P a = Unary();
//Node for unary operator
return(new NodePolUnary(a, Operation.UnaryMinus));
}
//Just return number if no unary operator is found
return(Part());
}
}
//Find and create the leaf with polynomial
Node_P Part()
{
//Polynomial
if (splitter.current_sign == Sign.Pol)
{
Node_P part = new NodePolynomial(splitter.pol); //create the node with found polynomial
splitter.Move_sign(); //move to the next sign
return(part);
}
//Parenthesis
if (splitter.current_sign == Sign.Open)
{
splitter.Move_sign(); //move to the next sign
//Parse sequentially all the expression after the (
Node_P part = PlusMinus();
// Find the )
if (splitter.current_sign != Sign.Close) //if there's no )
{
Console.WriteLine("Missing close parenthesis");
}
splitter.Move_sign(); //move to the next sign
return(part);
}
//If the sign is not classified
Console.WriteLine($"Unknown sign: {splitter.current_sign}");
throw new SystemException($"Unknown sign: {splitter.current_sign}");
}
//Method that parses the whole expression, which calls other methods one by one
//in order to build a correct binary tree of expression
public Node_P CheckExpression()
{
Node_P node = PlusMinus();
if (splitter.current_sign != Sign.EOF)
{
Console.WriteLine("Unexpected characters at end of expression");
Environment.Exit(0);
}
return(node);
}
Operation op; //operation between sides (eg. sum, substration, etc.)
//Constructor
public NodePolBinary(Node_P L, Node_P R, Operation O)
{
left = L;
right = R;
op = O;
}
public NodePolUnary(Node_P R, Operation O)
{
right = R;
op = O;
}
