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yap-6.3/C/mavar.c
vsc ab97812ec7 first steps to allow mavars with tabling
fix trailing for tabling with multiple get_cons


git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1356 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
2005-08-05 14:55:03 +00:00

273 lines
6.3 KiB
C

/*************************************************************************
* *
* YAP Prolog *
* *
* Yap Prolog was developed at NCCUP - Universidade do Porto *
* *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997 *
* *
**************************************************************************
* *
* File: mavar.c *
* Last rev: *
* mods: *
* comments: support from multiple assignment variables in YAP *
* *
*************************************************************************/
#include "Yap.h"
#ifdef MULTI_ASSIGNMENT_VARIABLES
#include "Yatom.h"
#include "Heap.h"
#include "eval.h"
STD_PROTO(static Int p_setarg, (void));
STD_PROTO(static Int p_create_mutable, (void));
STD_PROTO(static Int p_get_mutable, (void));
STD_PROTO(static Int p_update_mutable, (void));
STD_PROTO(static Int p_is_mutable, (void));
static Int
p_setarg(void)
{
CELL ti = Deref(ARG1), ts = Deref(ARG2);
Int i;
if (IsVarTerm(ti)) {
Yap_Error(INSTANTIATION_ERROR,ti,"setarg/3");
return(FALSE);
} else {
if (IsIntTerm(ti))
i = IntOfTerm(ti);
else {
union arith_ret v;
if (Yap_Eval(ti, &v) == long_int_e) {
i = v.Int;
} else {
Yap_Error(TYPE_ERROR_INTEGER,ti,"setarg/3");
return(FALSE);
}
}
}
if (IsVarTerm(ts)) {
Yap_Error(INSTANTIATION_ERROR,ts,"setarg/3");
} else if(IsApplTerm(ts)) {
CELL *pt;
if (IsExtensionFunctor(FunctorOfTerm(ts))) {
Yap_Error(TYPE_ERROR_COMPOUND,ts,"setarg/3");
return(FALSE);
}
if (i < 1 || i > (Int)ArityOfFunctor(FunctorOfTerm(ts))) {
if (i<0)
Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO,ts,"setarg/3");
return(FALSE);
if (i==0)
Yap_Error(DOMAIN_ERROR_NOT_ZERO,ts,"setarg/3");
return(FALSE);
}
pt = RepAppl(ts)+i;
/* the evil deed is to be done now */
MaBind(pt, Deref(ARG3));
} else if(IsPairTerm(ts)) {
CELL *pt;
if (i < 1 || i > 2) {
if (i<0)
Yap_Error(DOMAIN_ERROR_NOT_LESS_THAN_ZERO,ts,"setarg/3");
return(FALSE);
}
pt = RepPair(ts)+i-1;
/* the evil deed is to be done now */
MaBind(pt, Deref(ARG3));
} else {
Yap_Error(TYPE_ERROR_COMPOUND,ts,"setarg/3");
return(FALSE);
}
return(TRUE);
}
/* One problem with MAVars is that they you always trail on
non-determinate bindings. This is not cool if you have a long
determinate computation. One alternative could be to use
timestamps.
Because of !, the only timestamp one can trust is the trailpointer
(ouch..). The trail is not reclaimed after cuts. Also, if there was
a conditional binding, the trail is sure to have been increased
since the last choicepoint. For maximum effect, we can actually
store the current value of TR in the timestamp field, giving a way
to actually follow a link of all trailings for these variables.
*/
/* create and initialise a new timed var. The problem is: how to set
the clock?
If I give it the current value of B->TR, we may have trouble if no
non-determinate bindings are made before the next
choice-point. Just to make sure this doesn't cause trouble, if (TR
== B->TR) we will add a little something ;-).
*/
static Term
NewTimedVar(CELL val)
{
Term out = AbsAppl(H);
timed_var *tv;
*H++ = (CELL)FunctorMutable;
tv = (timed_var *)H;
RESET_VARIABLE(&(tv->clock));
tv->value = val;
H += sizeof(timed_var)/sizeof(CELL);
return(out);
}
Term
Yap_NewTimedVar(CELL val)
{
return NewTimedVar(val);
}
Term
Yap_NewEmptyTimedVar(void)
{
Term out = AbsAppl(H);
timed_var *tv;
*H++ = (CELL)FunctorMutable;
tv = (timed_var *)H;
RESET_VARIABLE(&(tv->clock));
RESET_VARIABLE(&(tv->value));
H += sizeof(timed_var)/sizeof(CELL);
return(out);
}
static Term
ReadTimedVar(Term inv)
{
timed_var *tv = (timed_var *)(RepAppl(inv)+1);
return(tv->value);
}
Term
Yap_ReadTimedVar(Term inv)
{
return ReadTimedVar(inv);
}
/* update a timed var with a new value */
static Term
UpdateTimedVar(Term inv, Term new)
{
timed_var *tv = (timed_var *)(RepAppl(inv)+1);
CELL t = tv->value;
CELL* timestmp = (CELL *)(tv->clock);
if (timestmp > B->cp_h
#if FROZEN_STACKS
&& timestmp > H_FZ
#endif
) {
/* last assignment more recent than last B */
#if SBA
if (Unsigned((Int)(tv)-(Int)(H_FZ)) >
Unsigned((Int)(B_FZ)-(Int)(H_FZ)))
*STACK_TO_SBA(&(tv->value)) = new;
else
#endif
tv->value = new;
} else {
Term nclock = (Term)H;
MaBind(&(tv->value), new);
*H++ = TermFoundVar;
MaBind(&(tv->clock), nclock);
}
return(t);
}
/* update a timed var with a new value */
Term
Yap_UpdateTimedVar(Term inv, Term new)
{
return UpdateTimedVar(inv, new);
}
static Int
p_create_mutable(void)
{
Term t = NewTimedVar(Deref(ARG1));
return(Yap_unify(ARG2,t));
}
static Int
p_get_mutable(void)
{
Term t = Deref(ARG2);
if (IsVarTerm(t)) {
Yap_Error(INSTANTIATION_ERROR, t, "get_mutable/3");
return(FALSE);
}
if (!IsApplTerm(t)) {
Yap_Error(TYPE_ERROR_COMPOUND,t,"get_mutable/3");
return(FALSE);
}
if (FunctorOfTerm(t) != FunctorMutable) {
Yap_Error(DOMAIN_ERROR_MUTABLE,t,"get_mutable/3");
return(FALSE);
}
t = ReadTimedVar(t);
return(Yap_unify(ARG1, t));
}
static Int
p_update_mutable(void)
{
Term t = Deref(ARG2);
if (IsVarTerm(t)) {
Yap_Error(INSTANTIATION_ERROR, t, "update_mutable/3");
return(FALSE);
}
if (!IsApplTerm(t)) {
Yap_Error(TYPE_ERROR_COMPOUND,t,"update_mutable/3");
return(FALSE);
}
if (FunctorOfTerm(t) != FunctorMutable) {
Yap_Error(DOMAIN_ERROR_MUTABLE,t,"update_mutable/3");
return(FALSE);
}
UpdateTimedVar(t, Deref(ARG1));
return(TRUE);
}
static Int
p_is_mutable(void)
{
Term t = Deref(ARG1);
if (IsVarTerm(t)) {
return(FALSE);
}
if (!IsApplTerm(t)) {
return(FALSE);
}
if (FunctorOfTerm(t) != FunctorMutable) {
return(FALSE);
}
return(TRUE);
}
#endif
void
Yap_InitMaVarCPreds(void)
{
#ifdef MULTI_ASSIGNMENT_VARIABLES
/* The most famous contributions of SICStus to the Prolog language */
Yap_InitCPred("setarg", 3, p_setarg, SafePredFlag);
Yap_InitCPred("create_mutable", 2, p_create_mutable, SafePredFlag);
Yap_InitCPred("get_mutable", 2, p_get_mutable, SafePredFlag);
Yap_InitCPred("update_mutable", 2, p_update_mutable, SafePredFlag);
Yap_InitCPred("is_mutable", 1, p_is_mutable, SafePredFlag);
#endif
}