public static ArithmeticLanguage FromTextDescriptions(List <String> alphabet, string symbolicStringText, string constraintText)
{
var symbolPattern = new Regex(@"^[a-zA-Z0-9]$");
var illegalSymbols = alphabet.FindAll(s => !symbolPattern.IsMatch(s));
if (illegalSymbols.Count > 0)
{
var message = string.Format(
"Found illegal symbols {0} in alphabet. Symbols should match [a-zA-Z0-9]",
string.Join(", ", illegalSymbols)
);
throw new PumpingLemmaException(message);
}
// Parse the language
var ss = PumpingLemma.Parser.parseSymbolicString(symbolicStringText, alphabet);
if (ss == null)
{
throw new PumpingLemmaException("Unable to parse language");
}
// Parse the constraintDesc
var constraint = PumpingLemma.Parser.parseCondition(constraintText);
if (constraint == null)
{
throw new PumpingLemmaException("Unable to parse constraint");
}
// Make sure all the variables are bound
var boundVariables = ss.GetIntegerVariables();
var constraintVariables = constraint.GetVariables();
// Console.WriteLine("Bound variables: " + String.Join(", ", boundVariables));
// Console.WriteLine("Constriant variables: " + String.Join(", ", constraintVariables));
foreach (var consVar in constraintVariables)
{
if (!boundVariables.Contains(consVar))
{
throw new PumpingLemmaException(
string.Format("Constraint variable {0} not bound", consVar));
}
}
// Add constraints saying that all variables are >= 0
BooleanExpression defaultConstraint = LogicalExpression.True();
foreach (var consVar in constraintVariables)
{
defaultConstraint = LogicalExpression.And(
defaultConstraint,
ComparisonExpression.GreaterThanOrEqual(
LinearIntegerExpression.SingleTerm(1, consVar),
LinearIntegerExpression.Constant(0)
)
);
}
return(new ArithmeticLanguage(alphabet, ss, constraint));
}
// Generates XML for the
public XElement SplitDisplayXML(
VariableType pumpingLength,
BooleanExpression additionalConstraints)
{
Contract.Assert(additionalConstraints.GetVariables().Count() <= 1);
if (additionalConstraints.GetVariables().Count == 1)
{
Contract.Assert(additionalConstraints.GetVariables().First().Equals(pumpingLength));
}
var pumpingLengthVariable = LinearIntegerExpression.SingleTerm(1, pumpingLength);
var repeatLengths = repeats();
// For great and inexplicable reasons. Trust me, it looks better this way.
var displayConstraints = LogicalExpression.And(repeatLengths.Select(x =>
ComparisonExpression.GreaterThanOrEqual(x, LinearIntegerExpression.Constant(5))
));
XElement symbstrings = new XElement("symbstrings");
foreach (var split in this.ValidSplits(pumpingLengthVariable, additionalConstraints))
{
var splitRepeatLengths = split.start.repeats();
splitRepeatLengths.AddRange(split.mid.repeats());
splitRepeatLengths.AddRange(split.end.repeats());
// Get models that don't look terrible
var splitDisplayConstraints = LogicalExpression.And(splitRepeatLengths.Select(x =>
ComparisonExpression.GreaterThanOrEqual(x, LinearIntegerExpression.Constant(1))
));
var constraint = LogicalExpression.And(displayConstraints, split.constraints, splitDisplayConstraints);
if (!constraint.isSatisfiable())
{
continue;
}
var splitModel = constraint.getModel();
var symbstr = new XElement("symbstr");
var strings = new XElement("strings");
var splits = new XElement("splits");
var constrs = new XElement("constraints");
Func <string, Tuple <int, int, SymbolicString>, XElement> handleSegment = (parentTagName, segment) => {
var parent = new XElement(parentTagName);
var from = new XElement("from"); from.Value = segment.Item1.ToString();
var to = new XElement("to"); to.Value = segment.Item2.ToString();
var label = new XElement("label"); label.Add(segment.Item3.ToDisplayXML());
parent.Add(from);
parent.Add(to);
parent.Add(label);
return(parent);
};
int strIndex = 0;
foreach (var segment in getSegments(splitModel, ref strIndex))
{
strings.Add(handleSegment("string", segment));
}
int splitIndex = 0;
foreach (var segment in new[] { split.start, split.mid, split.end })
{
splits.Add(handleSegment("split", segment.makeSegment(splitModel, ref splitIndex)));
}
var constr = new XElement("constraint");
constr.Add(split.constraints.ToDisplayXML());
constrs.Add(constr);
symbstr.Add(strings);
symbstr.Add(splits);
symbstr.Add(constrs);
symbstrings.Add(symbstr);
}
return(symbstrings);
}