c++ - 为任何 vector 编写 operator<< 的模板

Question

我正在尝试为任何可迭代容器编写模板运算符。得到一个奇怪的错误:

#include <iostream>

template <typename C>
std::ostream& operator<<(std::ostream& os, const C& c) {
  os << "[";
  for (const auto& v : c) {
    os << v << " ";
  }
  os << "]";
  return os;
}

vec.cc:5:6: error: use of overloaded operator '<<' is ambiguous (with operand types 'std::ostream' (aka 'basic_ostream') and 'const char [2]') os << "["; ~~ ^ ~~~

为什么会出现这个错误？我如何实现我想要的？

Answer 1

添加

template <typename C>
std::ostream& operator<<(std::ostream& os, const C& c) {
  os << "[";
  for (const auto& v : c) {
    os << v << " ";
  }
  os << "]";
  return os;
}

与其他人发生冲突global overloads的 operator << .

要解决这个问题，我们可以使用以下方法将您的模板限制为任何 vector 而不是任何类型

template <typename C>
std::ostream& operator<<(std::ostream& os, const std::vector<C>& c) {
  os << "[";
  for (const auto& v : c) {
    os << v << " ";
  }
  os << "]";
  return os;
}