def obfn_g1var(self):
        r"""Variable to be evaluated in computing the :math:`\ell_1`
        regularisation term, depending on the ``gEvalY`` option value.
        """

        # Use of self.block_sep1(self.AXnr) instead of self.cnst_A1(self.X)
        # reduces number of calls to self.cnst_A0
        return self.var_y1() if self.opt['gEvalY'] else \
            self.block_sep1(self.AXnr)