c++ - C++成员函数自定义类型返回 'does not name a type'错误

Question

在我的类中，我使用“using”关键字“bigvalue_t”声明了一个类型，并尝试创建一个返回相同类型 (to_vector) 的函数。我通过 gcc 返回了这个错误:

 g++ -g -O0 -Wall -Wextra -std=gnu++11 -c bigint.cpp
 bigint.cpp:45:1: error: ‘bigvalue_t’ does not name a type
 bigvalue_t bigint::to_vector (string& strval) {
 ^

这是我的头文件中的类:

class bigint {
  friend ostream& operator<< (ostream&, const bigint&);
private:
  long long_value {};
  using unumber = unsigned long;
  using digit_t = unsigned char;
  using bigvalue_t = vector<digit_t>;
  bool negative;
  bigvalue_t big_value;
  string to_string (unumber& num);
  bigvalue_t to_vector (string& strval);
  using quot_rem = pair<bigint,bigint>;
  friend quot_rem divide (const bigint&, const bigint&);
  friend void multiply_by_2 (unumber&);
  friend void divide_by_2 (unumber&);
public:

  //
  // Ensure synthesized members are genrated.
  //
  bigint() = default;
  bigint (const bigint&) = default;
  bigint (bigint&&) = default;
  bigint& operator= (const bigint&) = default;
  bigint& operator= (bigint&&) = default;
  ~bigint() = default;

  //
  // Extra ctors to make bigints.
  //
  bigint (const long);
  bigint (const string&);

这是我的构造函数和有问题的函数:

bigint::bigint (long that): long_value (that) {
   using digit_t = unsigned char;
   using bigvalue_t = vector<digit_t>;
   if (that < 0) this->negative = true;
   else this->negative = false;
   unumber that_value = that;
   string that_str = to_string (that_value);
   bigvalue_t bignum = to_vector (that_str);
   }

bigvalue_t bigint::to_vector (string& strval) {
   digit_t digi;
   bigvalue_t digivec;
   for (auto it = strval.rbegin(); it != rend; ++i) {
       digi = strval[it];
   digivec.push_back(digi);
   }
  return digivec;
}

任何有关正在发生的事情的想法都将不胜感激!它似乎没有接受我的类型定义。我被允许在早期的方法中使用我的另一个自定义变量“unumber”而没有错误，所以这让我挠头。

Answer 1

如注释中所述，使用

bigint::bigvalue_t bigint::to_vector (string& strval)
{
    // body
}

或者从 C++11 开始

auto bigint::to_vector (string& strval) -> bigvalue_t
{
    // body
}