Function string_not_empty

example/node2vec_randomwalk.cc:47–50

DEFINE_double(rate,        0.02,   "start 'rate'% walker per one bsp, reduce memory consumption");

bool string_not_empty(const char*, const std::string& value) {
  if (0 == value.length()) { return false; }
  return true;
}

DEFINE_validator(input,  &string_not_empty);