[英]fatal error LNK1120: 1 unresolved externals
I am compiling the following code and I am receiving an error. 我正在编译以下代码,但收到错误。 I want to practice templates in boost and I do not know how to handle this problem
我想在Boost中练习模板,但我不知道该如何处理
#include <stdafx.h>
#include <iostream>
#include <string>
#include <boost/function.hpp>
#include <boost/array.hpp>
using namespace std;
template<typename R,typename D>
class GenericFunction
{
private:
boost::function<R (D)> f;
protected:
GenericFunction();
public:
GenericFunction(const boost::function<R (D)>& myFunction);
R evaluate(const D& value) const ;
R operator ()(const D& value) const;
};
template <typename R, typename D, int N>
class ScalarValuedFunction:public GenericFunction<R,boost::array<D, N>>
{
public:
ScalarValuedFunction(const boost::function<R (const boost::array<D, N>)> &myF);
};
template<typename Numeric, std::size_t N>
Numeric Norm(const boost::array<Numeric , N>& Vec)
{
Numeric Result=Vec[0]*Vec[0];
for (std::size_t i=1; i<Vec.size();i++)
{
Result+=Vec[i]*Vec[i];
}
return Result;
}
int main ()
{
const int N=4;
boost::array<double, N> arr={0.2,.3,1.1,4};
ScalarValuedFunction<double, double, N> myfun(Norm<double,N>);
}
and receiving the following error, 并收到以下错误,
ConsoleApplication2.obj : error LNK2019: unresolved external symbol "public: __thiscall ScalarValuedFunction<double,double,4>::ScalarValuedFunction<double,double,4>(class boost::function<double __cdecl(class boost::array<double,4>)> const &)" (??0?$ScalarValuedFunction@NN$03@@QAE@ABV?$function@$$A6ANV?$array@N$03@boost@@@Z@boost@@@Z) referenced in function _main
1>c:\users\university\documents\visual studio 2012\Projects\ConsoleApplication2\Debug\ConsoleApplication2.exe : fatal error LNK1120: 1 unresolved externals
please someone tell me what is wrong with my code? 请有人告诉我我的代码有什么问题吗?
You did not provide a definition for your ScalarValuedFunction
class template's constructor, which is nevertheless declared in the class template's definition: 您没有为您提供一个定义
ScalarValuedFunction
类模板的构造函数,这是在类模板的定义仍然宣称 :
ScalarValuedFunction(const boost::function<R (const boost::array<D, N>)> &myF);
The linker therefore complains that the call to the constructor could not be resolved. 因此,链接器抱怨无法解决对构造函数的调用。 The call occurs in
main()
: 调用发生在
main()
:
ScalarValuedFunction<double, double, N> myfun(Norm<double,N>);
To fix your problem, add a definition for the constructor. 要解决您的问题,请为构造函数添加一个定义。 For instance:
例如:
template<typename R, typename D, int N>
ScalarValuedFunction<R, D, N:::ScalarValuedFunction(
const boost::function<R (const boost::array<D, N>)> &myF
)
:
GenericFunction<R, boost::array<D, N>>::GenericFunction(myMF)
{ }
您尚未为ScalarValuedFunction
类定义构造函数,仅对其进行了声明。
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