is-mbr(ket) sp returns |yes> if the coeff of ket in sp > 0, else |no> just a standard, set membership test ie, is the given ket a member of the given set represented by sp
is-mbr(|b>) split |abc> |yes> is-mbr(|c>) (0.3|a> + 2|b> + 9.7|c> + 13|d>) |yes> is-mbr(|x>) (0.3|a> + 2|b> + 9.7|c> + 13|d>) |no> friends |Fred> => |Jack> + |Harry> + |Ed> + |Mary> + |Rob> + |Patrick> + |Emma> + |Charlie> -- is Ed one of Fred's friends? is-mbr(|Ed>) friends |Fred> |yes> -- is Jane one of Fred's friends? is-mbr(|Jane>) friends |Fred> |no>