239 struct idf_iterator : public df_iterator<Inverse<T>, SetTy, External> {  struct
240   idf_iterator(const df_iterator<Inverse<T>, SetTy, External> &V)  in idf_iterator()  function
245 idf_iterator<T> idf_begin(const T& G) {  in idf_begin()
246   return idf_iterator<T>::begin(Inverse<T>(G));  in idf_begin()
250 idf_iterator<T> idf_end(const T& G){  in idf_end()
251   return idf_iterator<T>::end(Inverse<T>(G));  in idf_end()
256 iterator_range<idf_iterator<T>> inverse_depth_first(const T& G) {  in inverse_depth_first()
257   return iterator_range<idf_iterator<T>>(idf_begin(G), idf_end(G));  in inverse_depth_first()
262 struct idf_ext_iterator : public idf_iterator<T, SetTy, true> {
263   idf_ext_iterator(const idf_iterator<T, SetTy, true> &V)  in idf_ext_iterator()
264     : idf_iterator<T, SetTy, true>(V) {}  in idf_ext_iterator()
266     : idf_iterator<T, SetTy, true>(V) {}  in idf_ext_iterator()