$\forall$$T$:Type, $R_{1}$, $R_{2}$:($T$$\rightarrow$$T$$\rightarrow\mathbb{P}$). ($R_{1}$ $\Lleftarrow\!\Rrightarrow$\{$T$\} $R_{2}$) $\Rightarrow$ ($R_{1}$\^{}+ $\Lleftarrow\!\Rrightarrow$\{$T$\} $R_{2}$\^{}+)