// try to bind the variable associated with the last of search alternatives
// (t1|t2|...|tn) to the target term found matching one of these alternatives
bool TryBindingAltListVarToMatch (BaseTerm AltListVar, BaseTerm searchTerm, VarStack varStack)
{
if (AltListVar == null) return true;
return AltListVar.Unify (searchTerm, varStack);
}
// try to bind the range specification variable (if present) to the range last.
// if the minimun or the maximum range length was a variable, then bind it to the actual length just found
bool TryBindingRangeRelatedVars (ListPatternElem g, int rangeLength, ListTerm RangeList, VarStack varStack)
{
if (g.MinLenTerm.IsVar)
g.MinLenTerm.Unify (new DecimalTerm (rangeLength), varStack);
if (g.MaxLenTerm.IsVar)
g.MaxLenTerm.Unify (new DecimalTerm (rangeLength), varStack);
if (g.RangeBindVar != null)
{
if (RangeList == null) RangeList = ListTerm.EMPTYLIST;
if (!g.RangeBindVar.Unify (RangeList, varStack))
return false; // alas, the same range var was apparently used & bound earlier in the pattern
}
return true;
}
// each call processes one element of pattern[]
bool UnifyTailEx (int ip, int it, VarStack varStack)
{
ListPatternElem e = (ListPatternElem)pattern [ip];
Variable rangeSpecVar = (Variable)e.RangeBindVar;
NodeIterator subtreeIterator;
int k;
int marker;
ListTerm RangeList = null;
BaseTerm tail = null;
int minLen; // minimum required range length (number of range elements)
int maxLen; // maximum possible ...
if (!DoLowerAndUpperboundChecks (ip, it, out minLen, out maxLen)) return false;
// scan the minimal number of range elements. Add them to the range last,
// i.e. the last variable (if present) preceding the '{ , }'
for (int i = 0; i < minLen; i++)
{
if ((k = it + i) >= target.Count)
return false;
AppendToRangeList (ref RangeList, rangeSpecVar, target [k], ref tail);
}
marker = varStack.Count; // register the point to which we must possibly undo unifications
if (e.HasSearchTerm)
{
// scan the elements up to the maximum range length, and the element immediately thereafter
for (int i = minLen; i <= maxLen; i++)
{
BaseTerm t = null;
k = it + i;
if (k == target.Count) return false;
bool negSearchSucceeded = true; // iff none of the alternative term matches the target term
for (int j = 4; j < e.Args.Length; j++) // scan all AltSearchTerm alternatives (separated by '|')
{
BaseTerm searchTerm = e.AltSearchTerms [j];
DownRepFactor downRepFactor = null; // e.downRepFactor [j];
t = target [k];
AltLoopStatus status = AltLoopStatus.TryNextAlt;
if (downRepFactor == null)
{
status =
TryOneAlternative (ip, varStack, e, k, marker, RangeList, i, t, ref negSearchSucceeded, searchTerm);
if (status == AltLoopStatus.MatchFound) return true;
}
else // traverse the downRepFactor tree, which in principle may yield more than one match
{
subtreeIterator = new NodeIterator (t, searchTerm,
downRepFactor.minLenTerm, downRepFactor.maxLenTerm, downRepFactor.bindVar, varStack);
foreach (BaseTerm match in subtreeIterator) // try -- if necessary -- each tree match with the current search term
{
status =
TryOneAlternative (ip, varStack, e, k, marker, RangeList, i, match, ref negSearchSucceeded, searchTerm);
if (status == AltLoopStatus.MatchFound) return true;
if (status == AltLoopStatus.Break) break;
}
}
if (status == AltLoopStatus.Break) break;
}
// at this point sufficient alternatives have been tried
if (e.IsNegSearch && negSearchSucceeded) // none of the terms matched => ok if binding succeeds
{
if (!TryBindingAltListVarToMatch (e.AltListBindVar, t, varStack) || // bind the AltListBindVar to the match
!TryBindingRangeRelatedVars (e, i, RangeList, varStack)) // bind the range to the range variables
return false; // binding failed
if (ip == pattern.Length - 1) // this was the last pattern element
{
if (k == target.Count - 1) // both pattern and target exhausted
return true;
}
else if (UnifyTailEx (ip + 1, k + 1, varStack)) // now deal with the rest
return true;
}
else if (i < maxLen) // append the rejected term to the range last and go try the next term
AppendToRangeList (ref RangeList, rangeSpecVar, t, ref tail);
}
}
else // a range without a subsequent search term (so followed by another range or end of pattern)
{
for (int i = minLen; i <= maxLen; i++)
{
k = it + i;
if (k == target.Count) // ok, target[k] does not exist, end of target hit
return TryBindingRangeRelatedVars (e, i, RangeList, varStack); // i is actual range length
// k is ok
if (i < maxLen)
AppendToRangeList (ref RangeList, rangeSpecVar, target [k], ref tail);
// now deal with the rest
if (TryBindingRangeRelatedVars (e, i, RangeList, varStack) &&
UnifyTailEx (ip + 1, k, varStack)) return true;
}
}
// If we arrive here, no matching term was found in or immediately after the permitted range.
// Therefore, undo any unifications made locally in this method and return with failure.
if (marker != 0) BaseTerm.UnbindToMarker (varStack, marker);
return false;
}
private AltLoopStatus TryOneAlternative (int ip, VarStack varStack, ListPatternElem e, int k,
int marker, ListTerm RangeList, int i, BaseTerm t, ref bool negSearchSucceeded, BaseTerm searchTerm)
{
bool unified = searchTerm.Unify (t, varStack);
if (e.IsNegSearch) // none of the terms in the inner loop may match. ~(a | b | c) = ~a & ~b & ~c
{
if (unified) // ... no point in investigating the other alternatives if one does
{
negSearchSucceeded = false;
return AltLoopStatus.Break; // don't try the other alternatives
}
return AltLoopStatus.TryNextDown; // non of the downranges matches may lead to a success
}
else
{
if (unified && // we found a match. Unify, and
TryBindingAltListVarToMatch (e.AltListBindVar, t, varStack) && // bind the AltListBindVar to the match
TryBindingRangeRelatedVars (e, i, RangeList, varStack)) // bind the range to the range variables
{
if (ip == pattern.Length - 1) // this was the last pattern element
{
if (k == target.Count - 1) // both pattern and target exhausted
return AltLoopStatus.MatchFound;
}
else if (UnifyTailEx (ip + 1, k + 1, varStack)) // now deal with the rest
return AltLoopStatus.MatchFound;
}
// if we arrive here, it was not possible to ...
// (1) ... unify the range's SearchTerm with the target element, or
// (2) ... unify the range variable with the range last, or
// (3) ... successfully process the rest of the pattern and target
// Now unbind and try matching with the next target element
BaseTerm.UnbindToMarker (varStack, marker);
return AltLoopStatus.TryNextDown; // try the next downrange match
}
}
public override bool Unify (BaseTerm t, VarStack varStack)
{
NextUnifyCount ();
if (!((t = t.ChainEnd ()) is ListPatternElem)) return false; // should never occur
#if old
if (isNegSearch != ((ListPatternElem)t).isNegSearch) return false;
#endif
for (int i = 0; i < arity; i++)
if (!((args [i] == null && t.Args [i] == null) ||
args [i].Unify (t.Args [i], varStack))) return false;
return true;
}
public override bool Unify (BaseTerm t, VarStack varStack)
{
if ((t = t.ChainEnd ()) is Variable) // t not unified
{
((Variable)t).Bind (this);
varStack.Push (t);
return true;
}
if (t is ListPatternTerm && arity == t.Arity) // two ListPatternTerms match if their rangeTerms match
{
for (int i = 0; i < arity; i++)
if (!args [i].Unify (t.Args [i], varStack)) return false;
return true;
}
if (t is ListTerm)
{
pattern = args; // pattern is searched ...
target = ((ListTerm)t).ToList (); // ... in target
int ip = 0;
int it = 0;
return UnifyTailEx (ip, it, varStack);
}
return false;
}
public bool Retract(Term t, VarStack varStack, Term where)
{
string key = t.KbKey;
if (predefineds.Contains(key))
PrologIO.Error("retract of predefined predicate {0} not allowed", key);
PredicateDescr pd = this[key];
if (pd == null) return false;
#if persistent
if (pd is PersistentPredDescr)
{
((PersistentPredDescr)pd).Retract (t, varStack, where);
return true;
}
#endif
ClauseNode c = pd.GetClauseList(null, null);
ClauseNode prevc = null;
Term cleanTerm;
int top;
while (c != null)
{
cleanTerm = c.Term.CleanCopy();
top = varStack.Count;
if (cleanTerm.Unify(t, varStack)) // match found -- remove this term from the chain
{
if (prevc == null) // remove first clause
{
if (c.NextClause == null) // we are about to remove the last remaining clause for this predicate
{
predTable.Remove(key); // ... so remove its PredicateDescr as well
#if arg1index
pd.CreateFirstArgIndex (); // re-create
#endif
ResolveIndices();
}
else
pd.SetClauseListHead(c.NextClause);
}
else // not the first
{
prevc.NextClause = c.NextClause;
prevc = c;
pd.AdjustClauseListEnd();
#if arg1index
pd.CreateFirstArgIndex (); // re-create
#endif
}
return true; // possible bindings must stay intact (e.g. if p(a) then retract(p(X)) yields X=a)
}
Term s;
for (int i = varStack.Count - top; i > 0; i--) // unbind all vars that got bound by the above Unification
{
s = (Term)varStack.Pop();
s.Unbind();
}
prevc = c;
c = c.NextClause;
}
ResolveIndices();
return false;
}
public bool RetractAll(Term t, VarStack varStack) // should *always* return true ?????
{
// remark: first-argument indexing is not affected by deleting clauses
string key = t.KbKey;
if (predefineds.Contains(key))
PrologIO.Error("retract of predefined predicate {0} not allowed", key);
PredicateDescr pd = this[key];
if (pd == null) return true;
#if persistent
if (pd is PersistentPredDescr)
{
((PersistentPredDescr)pd).Retract (t, varStack, null);
return true; /////////////JPO persistent retract always to succeed ????
}
#endif
ClauseNode c = pd.GetClauseList(null, null);
ClauseNode prevc = null;
bool match = false;
while (c != null)
{
Term cleanTerm = c.Term.CleanCopy();
if (cleanTerm.Unifiable(t, varStack)) // match found -- remove this term from the chain
{
match = true; // to indicate that at least one term was found
if (prevc == null) // remove first clause
{
if (c.NextClause == null) // we are about to remove the last remaining clause for this predicate
{
predTable.Remove(key); // ... so remove its PredicateDescr as well
break;
}
else
pd.SetClauseListHead(c.NextClause);
}
else // not the first
{
prevc.NextClause = c.NextClause;
prevc = c;
}
}
else
prevc = c;
c = c.NextClause;
}
if (match)
{
#if arg1index
pd.DestroyFirstArgIndex (); // rebuild by ResolveIndices()
#endif
pd.AdjustClauseListEnd();
ResolveIndices();
}
return true;
}
public override void Retract (Term Term, VarStack stack, Term where)
{
StringBuilder deleteStat = new StringBuilder ("DELETE FROM " + dbEntity);
TableColumnCollection tcc = (TableColumnCollection)MetaDataCollection;
ListDictionary varNrs = new ListDictionary ();
bool first = true;
for (int i = 0; i < Term.Arity; i++)
{
Term arg = Term.Arg (i);
string colName = tcc [i].Name;
if (arg.IsAtom || arg.IsString)
deleteStat.AppendFormat ("{0} {1}={2}", Conj (ref first), colName, Utils.EnsureQuoted (arg.Functor));
else if (arg.IsNumber)
deleteStat.AppendFormat ("{0} {1}={2}", Conj (ref first), colName, arg.Functor);
else if (arg.IsVar)
{
object prevColNo;
// check whether value occurred as argument before (anonymous vars always have a unique varNo)
if ((prevColNo = varNrs [arg.VarNo]) != null) // ... yes
deleteStat.AppendFormat ("{0} {1}={2}", Conj (ref first), tcc [(int)prevColNo].Name, colName);
varNrs [arg.VarNo] = i; // save for comparison with next argument(s)
}
else if (!arg.IsVar)
IO.Error ("Illegal argument {0} for retract of persistent clause {1}", arg, Term);
}
if (where != null) // add the extra where-clause (if any)
{
// Copy the ref-table of column numers into a ref-table of corresponding column names
ListDictionary varNames = new ListDictionary (); // ... in-situ modifications of Collection-values is not possible
foreach (DictionaryEntry de in varNrs) varNames [(int)de.Key] = tcc [(int)de.Value].Name;
deleteStat.AppendFormat ("{0} {1}", Conj (ref first), where.ToStringSql (varNames));
}
if (first)
IO.Warning ("Retract -- DELETE without WHERE -- will NOT be executed !!!!!!!!");
else
ExecuteSqlCommand (deleteStat.ToString ());
}
public override void Retract (Term Term, VarStack stack, Term where)
{
IO.Error ("Unable to delete from '{0}' (not a table)", dbEntity);
}
public abstract void Retract (Term Term, VarStack stack, Term where);
public void NumberVars(ref int k, VarStack s)
{
Term t;
if (hasValue)
{
if (isUnified)
ULink.NumberVars(ref k, s);
else if (arity != 0) // hasValue & not isUnified
for (int i = 0; i < arity; i++) args[i].NumberVars(ref k, s);
}
else // unbound variable
{
Term a = new Term(k.ToString(), FType.number);
k++;
t = new Term("'$VAR'", a, OType.noop, 0);
this.Unify(t, s);
}
}
public bool Unifiable(Term t, VarStack varStack) // as Unify, but does not actually bind
{
int top = varStack.Count;
bool result = Unify(t, varStack);
for (int i = varStack.Count - top; i > 0; i--) // unbind all varNoSet that got bound by Unify
{
Term s = (Term)varStack.Pop();
s.Unbind();
}
return result;
}
public bool Unify(Term t, VarStack varStack, bool occurCheck)
{
if (isUnified) return ULink.Unify(t, varStack, occurCheck);
if (t.isUnified) return Unify(t.ULink, varStack, occurCheck);
//Interpreter.UCount++;
if (hasValue)
{
if (t.hasValue)
{
if (_functor.Equals(t._functor) && arity == t.Arity) // => two cuts will unify as well
{
for (int i = 0; i < arity; i++) if (!args[i].Unify(t.Arg(i), varStack, occurCheck)) return false;
return true;
}
else
return false;
}
// t is an unbound variable (add occur check here if deemed necessary)
t.Bind(this);
varStack.Push(t);
}
else // 'this' is an unbound variable. Add occur check here if deemed necessary
{
this.Bind(t);
varStack.Push(this);
}
return true;
}
// UNIFICATION
// The stack is used to store the variables and choice points that are bound by the unification.
// This is needed when backtracking. Unify does not do any unbinding in case of failure. This will
// be done when backtracking.
public bool Unify(Term t, VarStack varStack)
{
return Unify(t, varStack, false);
}