Eigen always eats the first two values

eigen_slice_eats_two.cpp

[mtao@ruemo ~/hg/testcode/c++/eigen/head]% cat main.cpp
#include <Eigen/Dense>
#include <iostream>
int main(int,char**)
{
    Eigen::Matrix<double,Eigen::Dynamic,1> x(20);
    std::iota(x.begin(),x.end(),0);
    // 0 1 2 3 4....
    std::cout << x.transpose() << std::endl;
    x = x.head(x.size()-1);
    // for some reason this consistently eats the first two values so you get
    // ~0 ~0 2 3 .... where ~0 seems to consistently be something like 1e-310
    std::cout << x.transpose() << std::endl;
    std::iota(x.begin(),x.end(),0);
    // Same thing now happens with new slices, but only for the first two elements
    x = x({0,1,2,3});
    std::cout << x.transpose() << std::endl;
    return 0;
}