isnum
if (isnum(x)) {
else if (isnum(y))
if (!isnum(vp)) { /* not a number */
} else if ((vp->tval & DONTFREE) != 0 || ! isnum(vp) || isfld(vp)) {
if (isnum)
bool isnum;
isnum = true;
isnum = false;
return (isnum ? 1 : -1);