/** @pred set_value(+ _A_,+ _C_)
Associate atom _A_ with constant _C_.
The `set_value` and `get_value` built-ins give a fast alternative to
the internal data-base. This is a simple form of implementing a global
counter.
~~~~~
read_and_increment_counter(Value) :-
get_value(counter, Value),
Value1 is Value+1,
set_value(counter, Value1).
~~~~~
This predicate is YAP specific.
*/
static Int p_setval(USES_REGS1) { /* '$set_value'(+Atom,+Atomic) */
Term t1 = Deref(ARG1), t2 = Deref(ARG2);
if (!IsVarTerm(t1) && IsAtomTerm(t1) &&
(!IsVarTerm(t2) && (IsAtomTerm(t2) || IsNumTerm(t2)))) {
Yap_PutValue(AtomOfTerm(t1), t2);
return (TRUE);
}
return (FALSE);
}
static Int p_values(USES_REGS1) { /* '$values'(Atom,Old,New) */
Term t1 = Deref(ARG1), t3 = Deref(ARG3);
if (IsVarTerm(t1)) {
Yap_Error(INSTANTIATION_ERROR, t1, "set_value/2");
return (FALSE);
}
if (!IsAtomTerm(t1)) {
Yap_Error(TYPE_ERROR_ATOM, t1, "set_value/2");
return (FALSE);
}
if (!Yap_unify_constant(ARG2, Yap_GetValue(AtomOfTerm(t1)))) {
return (FALSE);
}
if (!IsVarTerm(t3)) {
if (IsAtomTerm(t3) || IsNumTerm(t3)) {
Yap_PutValue(AtomOfTerm(t1), t3);
} else
return (FALSE);
}
return (TRUE);
}
static Term
Eval(Term t USES_REGS)
{
if (IsVarTerm(t)) {
return Yap_ArithError(INSTANTIATION_ERROR,t,"in arithmetic");
} else if (IsNumTerm(t)) {
return t;
} else if (IsAtomTerm(t)) {
ExpEntry *p;
Atom name = AtomOfTerm(t);
if (EndOfPAEntr(p = RepExpProp(Yap_GetExpProp(name, 0)))) {
/* error */
Term ti[2];
/* error */
ti[0] = t;
ti[1] = MkIntTerm(0);
t = Yap_MkApplTerm(FunctorSlash, 2, ti);
return Yap_ArithError(TYPE_ERROR_EVALUABLE, t,
"atom %s in arithmetic expression",
RepAtom(name)->StrOfAE);
}
return Yap_eval_atom(p->FOfEE);
} else if (IsApplTerm(t)) {
Functor fun = FunctorOfTerm(t);
if (fun == FunctorString) {
const char *s = StringOfTerm(t);
if (s[1] == '\0')
return MkIntegerTerm(s[0]);
return Yap_ArithError(TYPE_ERROR_EVALUABLE, t,
"string in arithmetic expression");
} else if ((Atom)fun == AtomFoundVar) {
return Yap_ArithError(TYPE_ERROR_EVALUABLE, TermNil,
"cyclic term in arithmetic expression");
} else {
Int n = ArityOfFunctor(fun);
Atom name = NameOfFunctor(fun);
ExpEntry *p;
Term t1, t2;
if (EndOfPAEntr(p = RepExpProp(Yap_GetExpProp(name, n)))) {
Term ti[2];
/* error */
ti[0] = t;
ti[1] = MkIntegerTerm(n);
t = Yap_MkApplTerm(FunctorSlash, 2, ti);
return Yap_ArithError(TYPE_ERROR_EVALUABLE, t,
"functor %s/%d for arithmetic expression",
RepAtom(name)->StrOfAE,n);
}
if (p->FOfEE == op_power && p->ArityOfEE == 2) {
t2 = ArgOfTerm(2, t);
if (IsPairTerm(t2)) {
return get_matrix_element(ArgOfTerm(1, t), t2 PASS_REGS);
}
}
*RepAppl(t) = (CELL)AtomFoundVar;
t1 = Eval(ArgOfTerm(1,t) PASS_REGS);
if (t1 == 0L) {
*RepAppl(t) = (CELL)fun;
return FALSE;
}
if (n == 1) {
*RepAppl(t) = (CELL)fun;
return Yap_eval_unary(p->FOfEE, t1);
}
t2 = Eval(ArgOfTerm(2,t) PASS_REGS);
*RepAppl(t) = (CELL)fun;
if (t2 == 0L)
return FALSE;
return Yap_eval_binary(p->FOfEE,t1,t2);
}
} /* else if (IsPairTerm(t)) */ {
if (TailOfTerm(t) != TermNil) {
return Yap_ArithError(TYPE_ERROR_EVALUABLE, t,
"string must contain a single character to be evaluated as an arithmetic expression");
}
return Eval(HeadOfTerm(t) PASS_REGS);
}
}
