I want to write a template function that only works for matrix with float(float/double in C++) type. How do I get the coefficient type of a matrix and check if it is an integer type or float type?

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template<typename Matrix> inline
void Covariance(const Matrix &mat) {
...;
}

you can use

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if (Eigen::internal::is_same<typename Matrix::Scalar float>::value) { ... }


is_same is a generic struct defined in Eigen as :

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template<typename T, typename U> struct is_same { enum { value = 0 }; };
template<typename T> struct is_same<T,T> { enum { value = 1 }; };


You can also look at NumTraits<typename MatrixType::Scalar>::IsInteger, ::IsComplex,, etc.