public List <Symbol> ConvertToPostfix(List <Symbol> list)
{
// This will be the final list of symbols
List <Symbol> result = new List <Symbol>();
// This will be a temporary stack for operators
Stack <Symbol> stack = new Stack <Symbol>();
foreach (Symbol t in list)
{
// Variable and Constant cant have children
if (t is Variable || t is Constant)
{
result.Add(t);
}
else if (t is OpeningBracket)
{
stack.Push(t);
}
else if (t is ClosingBracket)
{
try
{
Symbol arrival = stack.Pop();
while (arrival is OpeningBracket == false)
{
result.Add(arrival);
arrival = stack.Pop();
}
}
catch (InvalidOperationException)
{
throw new BracketsNotMatchingException();
}
}
else
{
while (stack.Count > 0)
{
if (t.Precedes(stack.Peek()))
{
break;
}
result.Add(stack.Pop());
}
stack.Push(t);
}
}
result.AddRange(stack.ToList());
return(result);
}
public List <Symbol> Collect(string text)
{
List <Symbol> symbols = new List <Symbol>();
for (int i = 0; i < text.Length; ++i)
{
if (Char.IsWhiteSpace(text[i]))
{
continue;
}
Symbol v = null;
Console.WriteLine(text[i] + " " + (int)text[i]);
Symbol t = SymbolFactory.GetSymbol(text[i]);
if (t == null)
{
t = SymbolFactory.GetSymbol(text, ref i);
if (t == null)
{
throw new Exception("Could not produce a symbol from string starting at position " + (i + 1));
}
}
if (t is Quantifier)
{
++i;
v = SymbolFactory.GetSymbol(text, ref i);
if (v == null)
{
throw new Exception("Invalid syntax after quantifier at position " + (i + 1));
}
if (v is Variable == false)
{
throw new QuantifierRefersToConstantException();
}
symbols.Add(v);
}
symbols.Add(t);
}
return(symbols);
}
public void Simplify()
{
bool actionTaken;
do
{
actionTaken = false;
List <Symbol.Symbol> symbolList = Top.ReverseBFS();
foreach (var symbol in symbolList)
{
if (symbol is Operator)
{
Symbol.Symbol left = symbol.GetChildren()[0];
Symbol.Symbol right = symbol.GetChildren()[1];
if (left is Variable && right is Variable)
{
if (left.Name == right.Name)
{
if (symbol.Name == "AND" || symbol.Name == "OR" || symbol.Name == "IMPLIES")
{
actionTaken = true;
Symbol.Symbol newSymbol = new Variable(name: left.Name);
if (symbol.Parent == null)
{
Top = newSymbol;
}
else
{
symbol.Parent.SetChild(symbol.IndexInParent, newSymbol);
}
}
}
}
}
}
} while (actionTaken);
}
