的boost :: multi_array的例子相当打印失败

Question

我有这样的聪明和冷静example：

#include <iostream> 
#include "boost/multi_array.hpp" 
#include "boost/array.hpp" 
#include "boost/cstdlib.hpp" 

template <typename Array> 
void print(std::ostream& os, const Array& A) 
{ 
    typename Array::const_iterator i; 
    os << "["; 
    for (i = A.begin(); i != A.end(); ++i) { 
    print(os, *i); 
    if (boost::next(i) != A.end()) 
     os << ','; 
    } 
    os << "]"; 
} 
void print(std::ostream& os, const double& x) 
{ 
    os << x; 
} 
int main() 
{ 
    typedef boost::multi_array<double, 2> array; 
    double values[] = { 
    0, 1, 2, 
    3, 4, 5 
    }; 
    const int values_size=6; 
    array A(boost::extents[2][3]); 
    A.assign(values,values+values_size); 
    print(std::cout, A); 
    return boost::exit_success; 
} 

但是，如果我尝试编译：G ++ -I/usr/include目录/升压/ b.cpp我得到这个错误：

b.cpp: In function ‘void print(std::ostream&, const Array&) [with Array = double]’: 
b.cpp:12: instantiated from ‘void print(std::ostream&, const Array&) [with Array = boost::detail::multi_array::const_sub_array<double, 1u, const double*>]’ 
b.cpp:12: instantiated from ‘void print(std::ostream&, const Array&) [with Array = main()::array]’ 
b.cpp:32: instantiated from here 
b.cpp:9: error: ‘double’ is not a class, struct, or union type 
b.cpp:11: error: request for member ‘begin’ in ‘A’, which is of non-class type ‘const double’ 
b.cpp:9: error: ‘double’ is not a class, struct, or union type 
b.cpp:9: error: request for member ‘end’ in ‘A’, which is of non-class type ‘const double’ 
b.cpp:9: error: ‘double’ is not a class, struct, or union type 
b.cpp:9: error: ‘double’ is not a class, struct, or union type 
b.cpp:9: error: ‘double’ is not a class, struct, or union type 
b.cpp:13: error: request for member ‘end’ in ‘A’, which is of non-class type ‘const double’ 
b.cpp:9: error: ‘double’ is not a class, struct, or union type 

shell returned 1 

什么错了？它似乎不了解第一个和第二个功能之间的差别打印功能。也许我错过了一些编译器选项？

编辑： 如果我使用模板<>作为Craig H答案我解决了孤立example.cpp中的问题。但是，如果我将2个函数放在我的项目中的单独.h文件中，则错误再次出现！

Answer 1

在本例中，您创建了一个模板函数作为您的第一个打印函数，然后声明了另一个函数，该函数实现了该模板的特定版本，而无需专门的模板。我认为，如果你更改以下行

void print(std::ostream& os, const double& x) 

到

template<> void print<double>(std::ostream& os, const double& x) 

您的问题就会消失。