ex_to<numeric>((*seq.begin()).coeff).is_equal(*_num1_p)) {
// *(+(x,y,...);c) -> +(*(x,c),*(y,c),...) (c numeric(), no powers of +())
const add & addref = ex_to<add>((*seq.begin()).rest);
ex_to<numeric>((*seq.begin()).coeff).is_equal(*_num1_p)) {
// *(+(x,y,...);c) -> +(*(x,c),*(y,c),...) (c numeric(), no powers of +())
const add & addref = ex_to<add>((*seq.begin()).rest);