Method impl

Core/Variational/var.cpp:598–601

et::var::impl funcs: */

/* et::var::impl funcs: */
impl::impl(const MatrixXd& _val) :
    val(_val),
    m_is_differentiable(false),
    op(op_type::none) {}

impl::impl(const MatrixXd& _val, bool is_differentiable) :
    val(_val),