EPNODE *
getE3(void) /* E3 -> E4 ^ E3 */
/* E4 */
{
EPNODE *ep1, *ep2;
ep1 = getE4();
if (nextc != '^')
return(ep1);
ep2 = newnode();
ep2->type = nextc;
scan();
addekid(ep2, ep1);
addekid(ep2, getE3());
if (esupport&E_RCONST) {
EPNODE *ep3 = ep1->sibling;
if (ep1->type == NUM && ep3->type == NUM) {
ep2 = rconst(ep2);
} else if (ep1->type == NUM && ep1->v.num == 0) {
epfree(ep3); /* (0 ^ E3) */
ep1->sibling = NULL;
efree((char *)ep2);
ep2 = ep1;
} else if ((ep3->type == NUM && ep3->v.num == 0) ||
(ep1->type == NUM && ep1->v.num == 1)) {
epfree(ep2); /* (E4 ^ 0) or (1 ^ E3) */
ep2 = newnode();
ep2->type = NUM;
ep2->v.num = 1;
}
}
return(ep2);
}
void
epfree( /* free a parse tree */
EPNODE *epar
)
{
EPNODE *ep;
switch (epar->type) {
case VAR:
varfree(epar->v.ln);
break;
case SYM:
freestr(epar->v.name);
break;
case NUM:
case CHAN:
case ARG:
case CLKT:
break;
default:
while ((ep = epar->v.kid) != NULL) {
epar->v.kid = ep->sibling;
epfree(ep);
}
break;
}
efree((char *)epar);
}
void
addchan( /* add an output channel assignment */
EPNODE *sp
)
{
int ch = sp->v.kid->v.chan;
EPNODE *ep, *epl;
for (epl = NULL, ep = outchan; ep != NULL; epl = ep, ep = ep->sibling)
if (ep->v.kid->v.chan >= ch) {
if (epl != NULL)
epl->sibling = sp;
else
outchan = sp;
if (ep->v.kid->v.chan > ch)
sp->sibling = ep;
else {
sp->sibling = ep->sibling;
epfree(ep);
}
return;
}
if (epl != NULL)
epl->sibling = sp;
else
outchan = sp;
sp->sibling = NULL;
}
void
dremove( /* delete all definitions of name */
char *name
)
{
EPNODE *ep;
while ((ep = dpop(name)) != NULL)
epfree(ep);
}
EPNODE *
getE2(void) /* E2 -> E2 MULOP E3 */
/* E3 */
{
EPNODE *ep1, *ep2;
ep1 = getE3();
while (nextc == '*' || nextc == '/') {
ep2 = newnode();
ep2->type = nextc;
scan();
addekid(ep2, ep1);
addekid(ep2, getE3());
if (esupport&E_RCONST) {
EPNODE *ep3 = ep1->sibling;
if (ep1->type == NUM && ep3->type == NUM) {
ep2 = rconst(ep2);
} else if (ep3->type == NUM) {
if (ep2->type == '/') {
if (ep3->v.num == 0)
syntax("divide by zero constant");
ep2->type = '*'; /* for speed */
ep3->v.num = 1./ep3->v.num;
} else if (ep3->v.num == 0) {
ep1->sibling = NULL; /* (E2 * 0) */
epfree(ep2);
ep2 = ep3;
}
} else if (ep1->type == NUM && ep1->v.num == 0) {
epfree(ep3); /* (0 * E3) or (0 / E3) */
ep1->sibling = NULL;
efree((char *)ep2);
ep2 = ep1;
}
}
ep1 = ep2;
}
return(ep1);
}
double
eval( /* evaluate an expression string */
char *expr
)
{
EPNODE *ep;
double rval;
ep = eparse(expr);
rval = evalue(ep);
epfree(ep);
return(rval);
}
void
dclear( /* delete variable definitions of name */
char *name
)
{
EPNODE *ep;
while ((ep = dpop(name)) != NULL) {
if (ep->type == ':') {
dpush(name, ep); /* don't clear constants */
return;
}
epfree(ep);
}
}
EPNODE *
rconst( /* reduce a constant expression */
EPNODE *epar
)
{
EPNODE *ep;
ep = newnode();
ep->type = NUM;
errno = 0;
ep->v.num = evalue(epar);
if (errno == EDOM || errno == ERANGE)
syntax("bad constant expression");
epfree(epar);
return(ep);
}
void
dcleanup( /* clear definitions (0->vars,1->output,2->consts) */
int lvl
)
{
int i;
VARDEF *vp;
EPNODE *ep;
/* if context is global, clear all */
for (i = 0; i < NHASH; i++)
for (vp = hashtbl[i]; vp != NULL; vp = vp->next)
if (incontext(vp->name)) {
if (lvl >= 2)
dremove(vp->name);
else
dclear(vp->name);
}
if (lvl >= 1) {
for (ep = outchan; ep != NULL; ep = ep->sibling)
epfree(ep);
outchan = NULL;
}
}
