func (self *Grammar) Follow(sym int) (s *set.Set) {
has := func(slice []int, i int) (bool, int) {
for j, v := range slice {
if v == i {
return true, j
}
}
return false, 0
}
s = set.New()
if sym == self.ORDER[0] {
s.Add(end)
}
for _, nt := range self.ORDER {
for _, p := range self.NTP[nt] {
if h, i := has(self.P[p], sym); h {
if i+1 < len(self.P[p]) {
f := self.First(self.P[p][i+1])
if f.Has(e) {
f.Remove(e)
s.Union(self.Follow(nt))
}
s.Union(f)
} else if i+1 == len(self.P[p]) && sym != nt {
s.Union(self.Follow(nt))
}
}
}
}
return s
}
func (self *Grammar) First(i int) (s *set.Set) {
s = set.New()
if self.ALL[i].Terminal {
s.Add(i)
return
}
for _, p := range self.NTP[i] {
all_e := true
for _, sym := range self.P[p] {
syms := self.First(sym)
s.Union(syms)
if !syms.Has(e) {
all_e = false
break
}
}
if all_e {
s.Add(e)
}
}
return
}
