POINTER st_ExistGen(CONTEXT IndexContext, st_INDEX StIndex, TERM Term)
/**************************************************************
INPUT:
RETURNS:
EFFECTS:
***************************************************************/
{
SYMBOL FirstDomain;
POINTER Result;
#ifdef CHECK
if (!st_StackEmpty(st_STACKSAVE)) {
misc_StartErrorReport();
misc_ErrorReport("\n In st_ExistGen: ST-Stack not empty.\n");
misc_FinishErrorReport();
}
else
if (st_CURRENT_RETRIEVAL != st_NOP) {
misc_StartErrorReport();
misc_ErrorReport("\n In st_ExistGen: %d Retrieval already in progress.\n",
st_CURRENT_RETRIEVAL);
misc_FinishErrorReport();
}
#endif
cont_Check();
if (st_Exist(StIndex)) {
st_CURRENT_RETRIEVAL = st_GEN;
st_WHICH_CONTEXTS = st_STANDARD;
st_INDEX_CONTEXT = IndexContext;
st_STACKSAVE = st_StackBottom();
FirstDomain = symbol_FirstIndexVariable();
cont_CreateBinding(IndexContext, FirstDomain, cont_InstanceContext(), Term);
cont_StartBinding();
st_StackPush(StIndex->subnodes);
cont_StartBinding();
Result = st_TraverseForExistGen(IndexContext);
#ifdef CHECK
cont_SaveState();
#endif
if (Result == NULL)
st_CancelExistRetrieval();
return Result;
} else
return NULL;
}
TERM cont_Deref(CONTEXT GlobalContext, CONTEXT* TermContext, TERM Term)
/******************************************************************
INPUT: A global context where the Index variables are bound,
a term <Term> and a call-by-ref context for <Term>.
RETURNS: The dereferenced term and the corresponding context.
SUMMARY: Dereferences bindings of variables.
CAUTION: In general, the context of the returned term <TermContext>
is different to the input context.
ASSUMPTION: All Index variables occuring in <Term> have to be
bound in <GlobalContext>,
no Index variable is mapped to another index variable
*******************************************************************/
{
if(term_IsIndexVariable(Term)) {
SYMBOL TermTop;
TermTop = term_TopSymbol(Term);
#ifdef CHECK
if(!cont_VarIsBound(GlobalContext, TermTop) ||
term_IsIndexVariable(cont_ContextBindingTerm(GlobalContext, TermTop))) {
misc_StartErrorReport();
misc_ErrorReport("\ncont_Deref: Illegal Context!");
misc_FinishErrorReport();
}
#endif
Term = cont_ContextBindingTerm(GlobalContext, TermTop);
*TermContext = cont_ContextBindingContext(GlobalContext, TermTop);
}
while (term_IsVariable(Term) && *TermContext != cont_InstanceContext()) {
SYMBOL TermTop;
TermTop = term_TopSymbol(Term);
if (cont_VarIsBound(*TermContext, TermTop)) {
CONTEXT HelpContext;
HelpContext = cont_ContextBindingContext(*TermContext, TermTop);
Term = cont_ContextBindingTerm(*TermContext, TermTop);
*TermContext = HelpContext;
}
else
return Term;
}
return Term;
}
LIST st_GetGenPreTest(CONTEXT IndexContext, st_INDEX StIndex, TERM Term)
/**************************************************************
INPUT:
RETURNS:
EFFECTS:
***************************************************************/
{
LIST Result;
SYMBOL FirstDomain;
cont_Check();
FirstDomain = symbol_FirstIndexVariable();
cont_CreateBinding(IndexContext, FirstDomain, cont_InstanceContext(), Term);
Result = st_TraverseTreeGenPreTest(IndexContext, StIndex, term_ComputeSize(Term));
cont_Reset();
return Result;
}
BOOL cont_TermEqualModuloBindings(CONTEXT IndexContext, CONTEXT CtL, TERM TermL,
CONTEXT CtR, TERM TermR)
/*********************************************************
INPUT: Two contexts, two terms.
RETURNS: The boolean value TRUE if the terms are equal.
CAUTION: EQUAL FUNCTION- OR PREDICATE SYMBOLS SHARE THE
SAME ARITY. THIS IS NOT VALID FOR JUNCTORS!
*******************************************************/
{
#ifdef CHECK
if (!(term_IsTerm(TermL) && term_IsTerm(TermR))) {
misc_StartErrorReport();
misc_ErrorReport("\n In cont_TermEqualModuloBindings: Input terms are corrupted.\n");
misc_FinishErrorReport();
}
#endif
while (term_IsVariable(TermL)) {
SYMBOL TermTop;
TermTop = term_TopSymbol(TermL);
if (symbol_IsIndexVariable(TermTop))
CtL = IndexContext;
else if (CtL == cont_InstanceContext())
break;
if (cont_VarIsBound(CtL, TermTop)) {
CONTEXT CHelp;
CHelp = cont_ContextBindingContext(CtL, TermTop);
TermL = cont_ContextBindingTerm(CtL, TermTop);
CtL = CHelp;
} else
break;
}
while (term_IsVariable(TermR)) {
SYMBOL TermTop;
TermTop = term_TopSymbol(TermR);
if (symbol_IsIndexVariable(TermTop))
CtR = IndexContext;
else if (CtR == cont_InstanceContext())
break;
if (cont_VarIsBound(CtR, TermTop)) {
CONTEXT CHelp;
CHelp = cont_ContextBindingContext(CtR, TermTop);
TermR = cont_ContextBindingTerm(CtR, TermTop);
CtR = CHelp;
} else
break;
}
if (!term_EqualTopSymbols(TermL, TermR))
return FALSE;
else
if (term_IsVariable(TermL)) {
if (CtL == CtR)
return TRUE;
else
return FALSE;
}
else
if (term_IsComplex(TermL)) {
LIST ScanL, ScanR;
for (ScanL=term_ArgumentList(TermL), ScanR=term_ArgumentList(TermR);
list_Exist(ScanL) && list_Exist(ScanR);
ScanL=list_Cdr(ScanL), ScanR=list_Cdr(ScanR))
if (!cont_TermEqualModuloBindings(IndexContext, CtL, list_Car(ScanL),
CtR, list_Car(ScanR)))
return FALSE;
return (list_Empty(ScanL) ? list_Empty(ScanR) : FALSE);
}
else
return TRUE;
}
