def _element_constructor_(self, x): """ TESTS:: sage: f(x) = x+1; g(y) = y+1 sage: f.parent()(g) x |--> y + 1 sage: g.parent()(f) y |--> x + 1 sage: f(x) = x+2*y; g(y) = y+3*x sage: f.parent()(g) x |--> 3*x + y sage: g.parent()(f) y |--> x + 2*y """ return SymbolicRing._element_constructor_(self, x)