Question

我正在使用Eigen线性代数包，它们提供了在尺寸上模板化的矩阵。我想有一些为我的程序生成测试数据的函数，所以我也试图在维度上对它们进行模板化，并且具有特定的特化：

template <size_t K>
boost::shared_ptr<std::vector<DistParams<K> > > sampleDistParams()
{
throw "not implemented";
}

template <size_t K>
boost::shared_ptr<std::vector<DistParams<K> > > sampleDistParams<1>()
{
boost::shared_ptr<std::vector<DistParams<K> > > distParams=(new std::vector<DistParams<K> >());
distParams->push_back(DistParams<K>(asMatrix(0.05), asMatrix(0.1)));
distParams->push_back(DistParams<K>(asMatrix(-0.1), asMatrix(0.2)));
return distParams;
}

template <size_t K>
boost::shared_ptr<std::vector<DistParams<K> > > sampleDistParams<2>()
{
boost::shared_ptr<std::vector<DistParams<K> > > distParams=(new std::vector<DistParams<K> >());
Eigen::Vector2d highMu;
lowMu << 0.04 << 0.06;
Eigen::Matrix2d lowSigma;
highSigma << 0.1 << 0.4
          << 0.4 << 0.12;

    Eigen::Vector2d lowMu;
lowMu << -0.08 << -0.12;
Eigen::Matrix2d highSigma;
highSigma << 0.2 << 0.7
          << 0.7 << 0.24;

distParams->push_back(DistParams<K>(highMu, lowSigma));
distParams->push_back(DistParams<K>(lowMu, highSigma));
return distParams;
}

然而，这个东西不能编译。我明白了：

/home/ga1009/PhD/cpp/pmi/cpp/test/baumiterationtest.cpp:24:73: error: template-id ‘sampleDistParams<1>’ in declaration of primary template
/home/ga1009/PhD/cpp/pmi/cpp/test/baumiterationtest.cpp:24:53: error: redefinition of ‘template<unsigned int K> boost::shared_ptr<std::vector<DistParams<K> > > {anonymous}::sampleDistParams()’
/home/ga1009/PhD/cpp/pmi/cpp/test/baumiterationtest.cpp:18:53: error: ‘template<unsigned int K> boost::shared_ptr<std::vector<DistParams<K> > > {anonymous}::sampleDistParams()’ previously declared here
/home/ga1009/PhD/cpp/pmi/cpp/test/baumiterationtest.cpp:33:73: error: template-id ‘sampleDistParams<2>’ in declaration of primary template
/home/ga1009/PhD/cpp/pmi/cpp/test/baumiterationtest.cpp:33:53: error: redefinition of ‘template<unsigned int K> boost::shared_ptr<std::vector<DistParams<K> > > {anonymous}::sampleDistParams()’
/home/ga1009/PhD/cpp/pmi/cpp/test/baumiterationtest.cpp:18:53: error: ‘template<unsigned int K> boost::shared_ptr<std::vector<DistParams<K> > > {anonymous}::sampleDistParams()’ previously declared here

出了什么问题，我该如何解决？

Answer 1

如果你想专门化一个功能模板，你不应该重新声明模板参数（注意你不能部分专门化一个功能模板）：

template<size_t K> void foo() { } // Primary template

template<size_t K> void foo<1>() { } // ERROR: Redefinition
template<> void foo<1>() { } // OK: Specialization

在您的特定情况下，模板专业化的正确签名是：

template<>
boost::shared_ptr<std::vector<DistParams<1> > > sampleDistParams<1>()

另请注意，在C ++ 11中，关闭尖括号（>）之间的空格不再是必需的。

Answer 2

语法错误：

模板专业化应该是：

template <>
boost::shared_ptr<std::vector<DistParams<K> > > sampleDistParams<1>()

函数模板特化（在int值上模板化）

2 个答案: