give the Isabelle proof the benefice of the doubt when the Isabelle theorem has fewer literals than the Metis one -- this makes a difference on lemma "Let (x::'a, y::'a) (inv_image (r::'b * 'b => bool) (f::'a => 'b)) = ((f x, f y) : r)" apply (metis in_inv_image mem_def)
(binary:application/x-msdos-program)