C ++：如何在孩子的基类列表中声明父模板的类型？

Question

我正在尝试使用g ++ 5.4.0编译我的基本c ++项目，但出现错误

       a     b   a1   b1
0    1.0   1.0  1.0  1.0
1    4.0   2.0  1.0  1.0
2    NaN   3.0  NaN  1.0
3    5.0   4.0  1.0  1.0
4   10.0   NaN  1.0  NaN
5   12.0   6.0  1.0  1.0
6    1.0   7.0  2.0  1.0
7    3.0   8.0  2.0  1.0
8    4.0   NaN  2.0  NaN
9    NaN  10.0  NaN  1.0
10   8.0  11.0  2.0  1.0
11  12.0  12.0  2.0  1.0

我已将其范围缩小为由定义基类的模板类型的方式引起的-如果删除模板及其所有相关成员函数并清除代码，则它将编译并运行。我不想定义BoolType的类型，因为我知道它总是布尔型的。我该如何正确地做到这一点？

datatype.h

df['a1'] = df[df.a.notnull()].a.diff().fillna(-1).lt(0).cumsum()
df['b1'] = df[df.b.notnull()].b.diff().fillna(-1).lt(0).cumsum()

datatype.cpp

undefined reference to DataType<bool>::DataType(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned short)'

booltype.h

#ifndef _DATATYPE_H_
#define _DATATYPE_H_

#include <string>

template<class T>
class DataType
{
  std::string const name;
  unsigned short const width;

public:
  DataType(std::string, unsigned short);
  std::string getName() const;
  unsigned short getWidth() const;
  virtual void toBytes(T, char[]) const = 0;
  virtual T fromBytes(char[]) const = 0;
  virtual T zero() const = 0;
};

#endif

booltype.cpp

#include <string>
#include "datatype.h"

template <class T>
DataType<T>::DataType(std::string name, unsigned short width)
  : name(name), width(width) {}

template <class T>
std::string DataType<T>::getName() const
{
  return this.name;
}

template <class T>
unsigned short DataType<T>::getWidth() const
{
  return this.width;
}

#ifndef _BOOLTYPE_H_ #define _BOOLTYPE_H_ #include "datatype.h" class BoolType : public DataType<bool> { public: BoolType(); void toBytes(bool, char[1]) const; bool fromBytes(char[1]) const; bool zero() const; }; #endif 的结果：

// booltype.cpp
#include <string>
#include <iostream>
#include "datatype.h"
#include "booltype.h"

BoolType::BoolType()
: DataType(std::string("BOOL"), 1) {}

void BoolType::toBytes(bool v, char b[1]) const
{
  b[0] = v ? 1 : 0;
}

bool BoolType::fromBytes(char b[1]) const
{
  return b[0] != 0;
}

bool BoolType::zero() const
{
  return false;
}

int main()
{
  char toBytesResult[1];
  BoolType BOOL;
  BOOL.toBytes(false, toBytesResult);
  std::cout << "toBytes(false): " << (int)toBytesResult[0] << std::endl;
  BOOL.toBytes(true, toBytesResult);
  std::cout << "toBytes(true): " << (int)toBytesResult[0] << std::endl;
  std::cout << "zero(): " << (int)BOOL.zero() << std::endl;
}