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yap-6.3/C/eval.c

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/*************************************************************************
* *
* YAP Prolog *
* *
* Yap Prolog was developed at NCCUP - Universidade do Porto *
* *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997 *
* *
**************************************************************************
* *
* File: eval.c *
* Last rev: *
* mods: *
* comments: arithmetical expression evaluation *
* *
*************************************************************************/
#ifdef SCCS
static char SccsId[] = "%W% %G%";
#endif
/*
* This file implements arithmetic operations
*
*/
#include "Yap.h"
#include "Yatom.h"
#include "YapHeap.h"
#include "eval.h"
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#if HAVE_STDARG_H
#include <stdarg.h>
#endif
#include <stdlib.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
static Term
Eval(Term t USES_REGS)
{
if (IsVarTerm(t)) {
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LOCAL_ArithError = TRUE;
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 */
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return Yap_ArithError(TYPE_ERROR_EVALUABLE, t,
"atom %s for arithmetic expression",
RepAtom(name)->StrOfAE);
}
return Yap_eval_atom(p->FOfEE);
} else if (IsApplTerm(t)) {
Functor fun = FunctorOfTerm(t);
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);
}
*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);
}
}
Term
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Yap_InnerEval(Term t)
{
CACHE_REGS
return Eval(t PASS_REGS);
}
#ifdef BEAM
Int BEAM_is(void);
Int
BEAM_is(void)
{ /* X is Y */
union arith_ret res;
blob_type bt;
bt = Eval(Deref(XREGS[2]), &res);
if (bt==db_ref_e) return (NULL);
return (EvalToTerm(bt,&res));
}
#endif
static Int
p_is( USES_REGS1 )
{ /* X is Y */
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Term out = 0L;
while (!(out = Eval(Deref(ARG2) PASS_REGS))) {
if (LOCAL_Error_TYPE == RESOURCE_ERROR_STACK) {
LOCAL_Error_TYPE = YAP_NO_ERROR;
if (!Yap_gcl(LOCAL_Error_Size, 2, ENV, CP)) {
Yap_Error(RESOURCE_ERROR_STACK, ARG2, LOCAL_ErrorMessage);
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return FALSE;
}
} else {
Yap_Error(LOCAL_Error_TYPE, LOCAL_Error_Term, LOCAL_ErrorMessage);
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return FALSE;
}
}
return Yap_unify_constant(ARG1,out);
}
Int
Yap_ArithError(yap_error_number type, Term where, char *format,...)
{
CACHE_REGS
va_list ap;
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LOCAL_ArithError = TRUE;
LOCAL_Error_TYPE = type;
LOCAL_Error_Term = where;
if (!LOCAL_ErrorMessage)
LOCAL_ErrorMessage = LOCAL_ErrorSay;
va_start (ap, format);
if (format != NULL) {
#if HAVE_VSNPRINTF
(void) vsnprintf(LOCAL_ErrorMessage, MAX_ERROR_MSG_SIZE, format, ap);
#else
(void) vsprintf(LOCAL_ErrorMessage, format, ap);
#endif
} else {
LOCAL_ErrorMessage[0] = '\0';
}
va_end (ap);
return 0L;
}
void
Yap_InitEval(void)
{
/* here are the arithmetical predicates */
Yap_InitConstExps();
Yap_InitUnaryExps();
Yap_InitBinaryExps();
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Yap_InitCPred("is", 2, p_is, 0L);
}