public TreeNode Parse(PositionQueue <IToken> pTokens)
{
/*
* 1.
* Get the first item and initialise the tree with it.
*/
TreeNode root = new TreeNode(pTokens.Dequeue());
/*
* 2.
* Currently the root node is also the current node.
* The current node is the node we currently lie on.
*/
TreeNode current = root;
while (pTokens.Count > 0)
{
/*
* 3.
* Get the next item.
* This will be called the new item.
*/
current = ProcessTokenToNode(pTokens.Dequeue(), current);
}
while (current.Parent != null)
{
current = current.Parent;
}
return(current);
}
private static void Main(string[] args)
{
while (true)
{
System.Console.Write("Please input the expression: ");
string lInput = System.Console.ReadLine();
try
{
Lexer lexer = new Lexer();
PositionQueue <IToken> tokens = lexer.Analyze(lInput);
foreach (IToken token in tokens.ToArray())
{
System.Console.WriteLine(token);
}
System.Console.ReadKey();
Parser parser = new Parser();
TreeNode tree = parser.Parse(tokens);
BTreePrinter.Print(tree);
System.Console.ReadKey();
double result = tree.Evaluate();
System.Console.WriteLine($" => {result}");
}
catch (Exception e)
{
System.Console.WriteLine($"{e.GetType().Name}: {e.Message}");
System.Console.WriteLine();
}
System.Console.ReadKey();
}
}
public double Evaluate(string pExpression)
{
try
{
PositionQueue <IToken> tokens = Lexer.Analyze(pExpression);
TreeNode treeNode = Parser.Parse(tokens);
return(treeNode.Evaluate());
}
catch (Exception e)
{
LastError = e;
throw new CouldNotEvaluateException(e);
}
}
public bool IsValid(string pExpression)
{
try
{
PositionQueue <IToken> tokens = Lexer.Analyze(pExpression);
TreeNode treeNode = Parser.Parse(tokens);
return(true);
}
catch (Exception e)
{
LastError = e;
}
return(false);
}
public PositionQueue <IToken> Analyze(string pInput)
{
Tokens = new PositionQueue <IToken>();
Chars = BuildQueue(pInput);
while (Chars.Count > 0)
{
IToken token = null;
if (IsWhitespace(Chars.Peek()))
{
Chars.Dequeue();
}
else if (IsDigit(Chars.Peek()))
{
token = ReadNumber();
}
else if (IsOperation(Chars.Peek()))
{
if (Tokens[Tokens.Count - 1].GetTokenType() == TokenType.Operator)
{
throw new NotImplementedException($"unexpected symbol \"{Chars.Dequeue()}\" at position {Chars.Position}");
}
else
{
token = ReadOperation();
}
}
else
{
throw new NotImplementedException($"unexpected symbol \"{Chars.Dequeue()}\" at position {Chars.Position}");
}
if (token != null)
{
Tokens.Enqueue(token);
}
}
return(Tokens);
}
