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从二维数组创建Eigen Map

c++c++11c++14eigen3
3
为什么这个有效？
typedef Matrix<double, N, N, RowMajor> Mat;
cout << Map<Mat>(&m[0][0]) << endl;

但这并不

cout << Map<Matrix<double, N, N, RowMajor>>(&m[0][0]) << endl;

你能否一行完成整个事情？

错误信息为：

eigen_playground.cpp:16:46: warning: use of right-shift operator ('>>') in template argument will require parentheses in
      C++11 [-Wc++11-compat]
    cout << Map<Matrix<double, N, N, RowMajor>>(&m[0][0]) << endl;
                                             ^
                                     (                   )
eigen_playground.cpp:16:46: error: invalid operands to binary expression ('int' and 'double *')
    cout << Map<Matrix<double, N, N, RowMajor>>(&m[0][0]) << endl;
                                     ~~~~~~~~^ ~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/istream:740:1: note: 
      candidate template ignored: could not match 'basic_istream<type-parameter-0-0, type-parameter-0-1>' against
      'Eigen::StorageOptions'
operator>>(basic_istream<_CharT, _Traits>& __is, _CharT* __s)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/istream:789:1: note: 
      candidate template ignored: could not match 'basic_istream<char, type-parameter-0-0>' against 'Eigen::StorageOptions'
operator>>(basic_istream<char, _Traits>& __is, unsigned char* __s)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/istream:797:1: note: 
      candidate template ignored: could not match 'basic_istream<char, type-parameter-0-0>' against 'Eigen::StorageOptions'
operator>>(basic_istream<char, _Traits>& __is, signed char* __s)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/istream:804:1: note: 
      candidate template ignored: could not match 'basic_istream<type-parameter-0-0, type-parameter-0-1>' against
      'Eigen::StorageOptions'
operator>>(basic_istream<_CharT, _Traits>& __is, _CharT& __c)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/istream:832:1: note: 
      candidate template ignored: could not match 'basic_istream<char, type-parameter-0-0>' against 'Eigen::StorageOptions'
operator>>(basic_istream<char, _Traits>& __is, unsigned char& __c)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/istream:840:1: note: 
      candidate template ignored: could not match 'basic_istream<char, type-parameter-0-0>' against 'Eigen::StorageOptions'
operator>>(basic_istream<char, _Traits>& __is, signed char& __c)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/istream:1506:1: note: 
      candidate template ignored: could not match 'basic_istream<type-parameter-0-0, type-parameter-0-1>' against
      'Eigen::StorageOptions'
operator>>(basic_istream<_CharT, _Traits>& __is,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/istream:1638:1: note: 
      candidate template ignored: could not match 'basic_istream<type-parameter-0-0, type-parameter-0-1>' against
      'Eigen::StorageOptions'
operator>>(basic_istream<_CharT, _Traits>& __is, bitset<_Size>& __x)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/complex:1369:1: note: 
      candidate template ignored: could not match 'basic_istream<type-parameter-0-1, type-parameter-0-2>' against
      'Eigen::StorageOptions'
operator>>(basic_istream<_CharT, _Traits>& __is, complex<_Tp>& __x)
^
eigen_playground.cpp:16:66: error: expected a type
    cout << Map<Matrix<double, N, N, RowMajor>>(&m[0][0]) << endl;
                                                                 ^
1 warning and 2 errors generated.
1
将右侧的 >> 与空格分开：> > - 273K
用这个符号 > >（代替 >>）将起作用。 - coder3101
1个回答
3
您遇到错误的原因是，在C++11之前，两个相邻的字符“>>”被强制解释为右移运算符。

由于您正在使用早于C++11的C++标准，请在这两个字符之间添加一个空格即可。

cout << Map< Matrix<double, N, N, RowMajor> >(&m[0][0]) << endl;
//                             right here. ^
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