Hi you all,

I've just included Eigen in many files of my project, but now I get this strange error in compilation time.

I've checked that is disappears iff I don't include #include <Eigen/SVD> or any other Eigen module, such as <Eigen/QR> or <Eigen/Eigenvalues>

./eigen/Eigen/src/Eigenvalues/Tridiagonalization.h:259: error: 'T' was not declared in this scope
../eigen/Eigen/src/Eigenvalues/Tridiagonalization.h:259: error: template argument 1 is invalid
../eigen/Eigen/src/Eigenvalues/Tridiagonalization.h:314: error: expected initializer before '<' token
../eigen/Eigen/src/Eigenvalues/RealSchur.h:155: error: 'T' was not declared in this scope
../eigen/Eigen/src/Eigenvalues/RealSchur.h:155: error: template argument 1 is invalid
../eigen/Eigen/src/Eigenvalues/RealSchur.h:155: error: abstract declarator 'const _MatrixType&' used as declaration
../eigen/Eigen/src/Eigenvalues/RealSchur.h:155: error: expected ';' before '(' token
../eigen/Eigen/src/Eigenvalues/RealSchur.h:178: error: expected `;' before 'RealSchur'
../eigen/Eigen/src/Eigenvalues/EigenSolver.h: In member function 'Eigen::EigenSolver<MatrixType>& Eigen::EigenSolver<_MatrixType>::compute(const _MatrixType&, bool)':
../eigen/Eigen/src/Eigenvalues/EigenSolver.h:370: error: 'T' was not declared in this scope
../eigen/Eigen/src/Eigenvalues/EigenSolver.h:370: error: expected primary-expression before ')' token
../eigen/Eigen/src/Eigenvalues/ComplexSchur.h: At global scope:
../eigen/Eigen/src/Eigenvalues/ComplexSchur.h:171: error: 'T' was not declared in this scope
../eigen/Eigen/src/Eigenvalues/ComplexSchur.h:171: error: template argument 1 is invalid
../eigen/Eigen/src/Eigenvalues/ComplexSchur.h:171: error: abstract declarator 'const Eigen::Matrix<std::complex<typename Eigen::NumTraits<typename Derived::Scalar>::Real>, Eigen::ComplexSchur<_MatrixType>::RowsAtCompileTime, Eigen::ComplexSchur<_MatrixType>::ColsAtCompileTime, Eigen::ComplexSchur<_MatrixType>::Options, Eigen::ComplexSchur<_MatrixType>::MaxRowsAtCompileTime, Eigen::ComplexSchur<_MatrixType>::MaxColsAtCompileTime>&' used as declaration
../eigen/Eigen/src/Eigenvalues/ComplexSchur.h:171: error: expected ';' before '(' token
../eigen/Eigen/src/Eigenvalues/ComplexSchur.h:196: error: expected `;' before 'ComplexSchur'
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h: In member function 'Eigen::ComplexEigenSolver<MatrixType>& Eigen::ComplexEigenSolver<_MatrixType>::compute(const _MatrixType&, bool)':
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:262: error: 'T' was not declared in this scope
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:262: error: expected primary-expression before ')' token
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h: In member function 'void Eigen::ComplexEigenSolver<_MatrixType>::doComputeEigenvectors(typename Eigen::NumTraits<typename Derived::Scalar>::Real)':
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:288: error: 'T' was not declared in this scope
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:288: error: template argument 1 is invalid
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:290: error: 'T' cannot appear in a constant-expression
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:290: error: template argument 1 is invalid
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:291: error: 'T' cannot appear in a constant-expression
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:291: error: template argument 1 is invalid
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:291: error: 'T' cannot appear in a constant-expression
../eigen/Eigen/src/Eigenvalues/ComplexEigenSolver.h:291: error: template argument 1 is invalid


Mac OSX Leopard 10.5.8
g++ --version:
i686-apple-darwin9-g++-4.0.1 (GCC) 4.0.1 (Apple Inc. build 5493)
Eigen 3.0 beta2

very strange.

This is the code of a KernelPCA dimensionality reduction class:
######### KernelPCA.cpp ######
#include "KernelPCA.h"
#include <Eigen/Core>
//#include <Eigen/SVD> // why can't I include SVD???
KernelPCA::KernelPCA()
{

}

######### KernelPCA.h ######
#ifndef _KERNELPCA_H_
#define _KERNELPCA_H_

#include "DimensionalityReduction.h"


using namespace std;

class KernelPCA : public DimensionalityReduction
{
private:
GraphLayout *g;
double epsilon; // create an edge iff ||x_i - x_j|| < epsilon
int kappa; // choose the K-nearest neighbors

public:
KernelPCA();
};

#endif


Thank you!

First I had to include <Eigen/SVD> and then my specific headers files...

Perhaps you should check that the header files you include before Eigen does not define **** macros...