/* Replace the variables describing the state <from> with the ones that describe
* state <to>
*/
public static FormulaNode Substitute(FormulaNode formula, SymbolicState from, SymbolicState to)
{
if (formula.GetLogicOperator() == LogicOperator.VAR)
{
if (from.nameToElementary.Keys.Contains(formula.GetName()))
{
// this variable represents an elementary formula
var elementary = from.nameToElementary[formula.GetName()];
return(new FormulaNode(to.elementaryNames[elementary]));
}
else
{
return(new FormulaNode(formula.GetName()));
}
}
if (formula.GetLogicOperator() == LogicOperator.ALL ||
formula.GetLogicOperator() == LogicOperator.EXISTS)
{
FormulaNode result = new FormulaNode(formula.GetLogicOperator());
if (from.nameToElementary.Keys.Contains(formula.GetName()))
{
// this variable represents an elementary formula
var elementary = from.nameToElementary[formula.GetName()];
result.SetName(to.elementaryNames[elementary]);
}
else
{
result.SetName(formula.GetName());
}
result.SetChildren(Substitute(formula[0], from, to), null);
return(result);
}
FormulaNode res = new FormulaNode(formula.GetLogicOperator());
FormulaNode left = Substitute(formula[0], from, to);
FormulaNode right = null;
if (formula[1] != null)
{
right = Substitute(formula[1], from, to);
}
res.SetChildren(left, right);
return(res);
}
public FormulaNode Quantify(LogicOperator quantifier, FormulaNode formula)
{
FormulaNode result = formula;
foreach (string name in elementaryNames.Values)
{
result = new FormulaNode(quantifier, result, null);
result.SetName(name);
}
return(result);
}
private static FormulaNode Parse(List <Token> tokens)
{
FormulaNode result = null;
List <Token> rightSide = new List <Token>();
BinaryToken lastOp = null;
// the input is a single token - must be an atom or an unparsed string
if (tokens.Count == 1)
{
var tok = tokens[0] as LiteralToken;
if (tok.type == TokenType.ATOM)
{
return(new FormulaNode(tok.value));
}
return(Parse(ToplevelTokenize(tok.value)));
}
int minPrecedence = MAX_PRECEDENCE;
for (int i = 0; i < tokens.Count; i++)
{
if (tokens[i] is BinaryToken)
{
var op = tokens[i] as BinaryToken;
minPrecedence = Math.Min(minPrecedence, op.precedence);
}
}
if (minPrecedence == MAX_PRECEDENCE)
{
// the input didn't contain any toplevel binary operators
var opToken = tokens[0] as UnaryToken;
result = new FormulaNode(opToken.logicOperator);
var operand = Parse(tokens.GetRange(1, tokens.Count - 1));
if (untilOperators.Contains(opToken.logicOperator))
{
result.SetChildren(operand[0], operand[1]);
}
else if (quanitifers.Contains(opToken.logicOperator))
{
result.SetName(operand[0].GetName());
result.SetChildren(operand[1], null);
}
else
{
result.SetChildren(operand, null);
}
return(result);
}
// if we got here - split by lowest-precedence binary operator
foreach (Token t in tokens)
{
if (t is BinaryToken)
{
var op = t as BinaryToken;
if (op.precedence == minPrecedence)
{
if (result == null)
{
result = Parse(rightSide);
}
else
{
var leftSide = result;
result = new FormulaNode(lastOp.logicOperator);
result.SetChildren(leftSide, Parse(rightSide));
}
rightSide = new List <Token>();
lastOp = op;
continue;
}
}
rightSide.Add(t);
}
if (rightSide.Count != 0)
{
var leftSide = result;
result = new FormulaNode(lastOp.logicOperator);
result.SetChildren(leftSide, Parse(rightSide));
}
return(result);
}