Question

编译并执行以下文件没有任何问题。当我从 Ode.cpp 中的aos::函数前面删除euler时，编译器会抛出以下错误。

Ode.cpp:13: undefined reference to `aos::euler(std::vector<double, std::allocator<double> >* (*)(std::vector<double, std::allocator<double> >*, unsigned int, unsigned int), std::vector<double, std::allocator<double> >*, unsigned int, unsigned int)'
collect2: error: ld returned 1 exit status

为什么这样做？我已经在Ode的定义和实现文件中定义了namespace。

干杯， MrMcKizzle

Ode.hpp

#include <SDL2/SDL.h>
#include <vector>
#include <iostream>
#include <string>

#ifndef ODE_HPP
#define ODE_HPP


namespace aos 
{ 
    std::vector< double > * euler(
        std::vector< double > * (*)(std::vector< double > *, Uint32, Uint32),
        std::vector< double > * x, Uint32 dt, Uint32 t
    );

    class Integrator {
        public:
            Integrator();
            //~Integrator();
            std::vector< double > * (*integrator)(
                std::vector< double > * (*)(std::vector< double > *, Uint32, Uint32),
                std::vector< double > * x, Uint32 dt, Uint32 t) = euler;  ///< Stores a pointer to the default ODE integrator function (defaults to euler)   
            std::vector< double > * integrate(
                std::vector< double > * (*)(std::vector< double > *, Uint32, Uint32),
                std::vector< double > * x, Uint32 dt, Uint32 t
            );
    };
}
#endif

Ode.cpp

using namespace aos;

std::vector< double > * aos::euler(
    std::vector< double > * (*f)(std::vector< double > *, Uint32, Uint32),
    std::vector< double > * x, Uint32 dt, Uint32 t)
{ 
    std::cout << "aos::euler" << std::endl;
    return f(x, dt, t);
}

Integrator::Integrator(){}

std::vector< double > * Integrator::integrate(
    std::vector< double > * (*f)(std::vector< double > *, Uint32, Uint32),
    std::vector< double > * x, Uint32 dt, Uint32 t)
{
    std::cout << "Integrator::integrate" << std::endl;
    return this->integrator(f, x, dt, t);
}

的main.cpp

#include "Ode.hpp"

#include <SDL2/SDL.h>
#include <vector>
#include <iostream>
#include <string>

std::vector< double > * dummysys(std::vector< double > * x, Uint32 dt, Uint32 t)
{
    cout << "main.cpp::dummysys" << endl;

    return new vector< double >();
}


int main(int argc, char **argv)
{
    aos::Integrator * intgr = new aos::Integrator();

    vector< double > x;
    //integrate(dummysys, &x, 16, 123);
    intgr->integrate(dummysys, & x, 16, 123);

    return 0;
}

Answer 1

在您的cpp中，将您的实现包含在命名空间aos中，就像在hpp。

中一样

namespace aos
{
std::vector< double > * euler(
    std::vector< double > * (*f)(std::vector< double > *, Uint32, Uint32),
    std::vector< double > * x, Uint32 dt, Uint32 t)
{ 
    std::cout << "aos::euler" << std::endl;
    return f(x, dt, t);
}

Integrator::Integrator(){}

std::vector< double > * Integrator::integrate(
    std::vector< double > * (*f)(std::vector< double > *, Uint32, Uint32),
    std::vector< double > * x, Uint32 dt, Uint32 t)
{
    std::cout << "Integrator::integrate" << std::endl;
    return this->integrator(f, x, dt, t);
}
}

您可以使用main.cpp中的using namespace aos

为什么要重新定义函数命名空间？

Ode.hpp

Ode.cpp

的main.cpp

1 个答案: