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/*======================================================================
APEQC(c,k,P)
Apply equational constraints.
Inputs
c : a cell over which a stack has just been constructed.
k : the level of c.
P : the list of projection factors.
Output
None.
Effect
If there are no (k+1)-level constraints nothing is done.
Otherwise each cell of the stack over c which fails to satisfy
each k-level constraint has its truth value set to FALSE and its
HOWTV field set to BYEQC.
======================================================================*/
#include "qepcad.h"
void QepcadCls::APEQC(Word c, Word k, Word P)
{
Word c1,E,E1,E11,Ep,Ep1,i,j,m,M,Mp,S,t,Ps,p;
Step1: /* Get (k+1)-level equational constraints, if none, return. */
E = LELTI(GVEQNCONST,k+1);
if (E == NIL) return;
Step2: /* Get the stack over c. */
S = LELTI(c,CHILD);
Step3: /* Get the next cell in stack with undetermined truth value. */
if (S != NIL)
ADV(S,&c1,&S);
else
goto Return;
t = LELTI(c1,TRUTH);
if (t != UNDET)
goto Step3;
Step4: /* Get the signature list of the cell. */
M = LELTI(c1,SIGNPF);
Step5: /* Initialize the constraint list. */
Ep = E;
Step6: /* Get the next constraint, if any, and initialize it;*/
/* else return. */
if (Ep == NIL)
goto Step3;
else {
ADV(Ep,&E1,&Ep);
Ep1 = E1; }
Step7: /* Get the level and index of the next element of the constraint,
if any; else set truth value of cell to FALSE and return for next cell. */
if (Ep1 == NIL) {
SLELTI(c1,TRUTH,FALSE);
SLELTI(c1,HOWTV,BYEQC);
if (k < GVNFV) GVEQN2A = SUNION(GVEQN2A,LIST1(E));
goto Step3; }
else {
ADV(Ep1,&E11,&Ep1);
i = SECOND(E11);
j = THIRD(E11); }
Step8: /* Check whether P_i,j is zero in c1. */
Mp = LELTI(M,k + 2 - i);
Ps = LELTI(P,i);
while (Mp != NIL) {
ADV(Mp,&m,&Mp);
ADV(Ps,&p,&Ps);
if (m == 0 && THIRD(LELTI(p,PO_LABEL)) == j)
goto Step6; }
goto Step7;
Return: /* Prepare for return. */
return;
}
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