RingHom($R$;$S$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\{$f$:$\mid$$R$$\mid\rightarrow\mid$$S$$\parallel$ FunThru2op($\mid$$R$$\mid$;$\mid$$S$$\mid$;+$R$;+$S$;$f$) \& FunThru2op($\mid$$R$$\mid$;$\mid$$S$$\mid$;$\ast$;$\ast$;$f$) \& $f$(1) = 1\}