BOOL res_HasTautology(CLAUSE clause)
/**********************************************************
INPUT: A clauses.
RETURNS: TRUE if the clause contains a complementary
literal pair and FALSE otherwise.
CAUTION: None.
***********************************************************/
{
BOOL found;
TERM literal1;
int i, j, n;
found = FALSE;
n = clause_Length(clause);
for (i = 0; i < n && !found; i++) {
literal1 = fol_ComplementaryTerm(clause_GetLiteralTerm(clause,i));
for (j = 0; j < n && !found; j++)
if (j != i && term_Equal(literal1, clause_GetLiteralTerm(clause,j)))
found = TRUE;
term_Delete(literal1);
}
return found;
}
static ord_RESULT kbo_CompareStruc(TERM Term1, TERM Term2, int WeightDiff)
/**************************************************************
INPUT: Two terms where the kbo-variable condition for <Term1> and
<Term2> is satisfied and <WeightDiff> is the kbo weight difference
between <Term1> and <Term2>
RETURNS: ord_UNCOMPARABLE, if Term1 and Term2 are uncomparable
ord_EQUAL, if Term1 and Term2 are equal
ord_GREATER_THAN, if Term1 is greater than Term2
CAUTION: The precedence from the order module is used to determine
the precedence of symbols!
***************************************************************/
{
LIST Scan1,Scan2;
SYMBOL Top1,Top2;
Top1 = term_TopSymbol(Term1);
Top2 = term_TopSymbol(Term2);
if (WeightDiff > 0)
return ord_GREATER_THAN;
else if (WeightDiff == 0) {
if (symbol_IsStandardVariable(Top1)) {
if (symbol_IsStandardVariable(Top2))
return ord_EQUAL;
else
return ord_UNCOMPARABLE;
}
else if (symbol_IsStandardVariable(Top2) ||
symbol_PrecedenceGreater(ord_PRECEDENCE, Top1, Top2))
return ord_GREATER_THAN;
else if (Top1 == Top2) {
int RecWeightDiff;
BOOL T1VarCond, T2VarCond;
TERM RecTerm1,RecTerm2;
Scan1 = term_ArgumentList(Term1);
Scan2 = term_ArgumentList(Term2);
if (symbol_HasProperty(Top1,ORDRIGHT)) {
int i;
for (i = symbol_Arity(Top1);
i > 0 && term_Equal(list_NthElement(Scan1,i),list_NthElement(Scan2,i));
i--);
if (i > 0) {
RecTerm1 = (TERM)list_NthElement(Scan1,i);
RecTerm2 = (TERM)list_NthElement(Scan2,i);
}
else
return ord_EQUAL;
}
else {
while (!list_Empty(Scan1) && term_Equal(list_Car(Scan1),list_Car(Scan2))) {
Scan1 = list_Cdr(Scan1);
Scan2 = list_Cdr(Scan2);
}
if (list_Empty(Scan1)) /* Implies that list_Empty(Scan2) */
return ord_EQUAL;
else {
RecTerm1 = (TERM)list_Car(Scan1);
RecTerm2 = (TERM)list_Car(Scan2);
}
}
RecWeightDiff = kbo_CompVarCondAndWeight(RecTerm1,&T1VarCond,RecTerm2,&T2VarCond);
if (RecWeightDiff >= 0 && T1VarCond)
return kbo_CompareStruc(RecTerm1, RecTerm2, RecWeightDiff);
else
return ord_UNCOMPARABLE;
}
else
return ord_UNCOMPARABLE;
}
else
return ord_UNCOMPARABLE;
return ord_UNCOMPARABLE;
}
